Kaplan & Khan Academy Discrete (CHEMISTRY)

Which of the following is the correct electron configuration for Zn2+? A. 1s2 2s2 2p6 3s2 3p6 4s0 3d10 B. 1s2 2s2 2p6 3s2 3p6 4s2 3d8 C. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 D. 1s2 2s2 2p6 3s2 3p6 4s0 3d8

A. 1s2 2s2 2p6 3s2 3p6 4s0 3d10 - Remember that when electrons are removed from an element, forming a cation, they will be removed from the subshell with the HIGHEST n value first. Zn0 has 30 electrons, so it would have an electron configuration of 1s2 2s2 2p6 3s2 3p6 4s2 3d10. The 4s subshell has the highest principle quantum number, so it is emptied first, forming 1s2 2s2 2p6 3s2 3p6 4s0 3d10. (B) implies that the electrons are pulled out of the d subshell, (C) presents the configuration of the uncharged normal zinc atom, and (D) shows the configuration that would exist if four electrons were removed.

The equilibrium constant (Keq) of a reaction will change in response to which of the following? A. A change in temperature B. Addition of products C. Addition of reactants or products D. Addition of a catalyst

A. Change in temperature - The equilibrium constant is a thermodynamic parameter that depends on the temperature of the system.

Which of the following combinations of liquids would be expected to have a vapor pressure higher than the vapor pressure that would be predicted by Raoult's Law? A. Ethanol and hexane B. Acetone and water C. Isopropanol and methanol D. Nitric acid and water

A. Ethanol and hexane - Mixtures that have a higher vapor pressure than predicted by Raoult's Law have stronger solvent-solvent and solute-solute interactions than solvent-solute interactions. Therefore, particles do not want to stay in solution and more readily evaporate, creating a higher vapor pressure than an ideal solution. Two liquids that have different properties, like hexane (hydrophobic) and ethanol (hydrophilic, small) in (A), would not have many interactions with each other and would cause positive deviation; i.e. higher vapor pressure. (B) and (C) are composed of liquids that are similar to one another and would not show significant deviation from Raoult's Law. (D) contains two liquids that would interact very well with each other, which would actually cause a negative deviation from Raoult's Law--when attracted to one another, solutes and solvents prefer to stay in liquid form and have a lower vapor pressure than predicted by Raoult's Law.

Consider the following data: o Hg^2+ + 2e -----> Hg ; E°red = +0.85 V o Cu^+ + e --------> Cu ; E°red = +0.52 V o Zn^2+ + 2e -------> Zn ; E°red = -0.76 V o Al^3+ + 3e -------> Al ; E°red = -1.66 V The anode of a certain galvanic cell is composed of copper. Which of the metals from the data table can be used at the cathode, assuming equal concentrations of two electrolyte solutions? A. Hg (mercury) B. Cu (copper) C. Zn (zinc) D. Al (aluminum)

A. Hg (mercury) - Oxidation occurs at the anode, and reduction occurs at the cathode. Because Cu is the anode, it must be oxidized. The reduction potential of the cathode cannot be less than that of the anode for a galvanic cell. Therefore, mercury, (A), must be the cathode. In a concentration cell, the same material is used as both the cathode and anode; however, this question assumes equal concentrations. If both electrolyte solutions have the same concentration, there will be no oxidation-reduction reaction and, therefore, no anode or cathode. This eliminates (B).

Which of the following sets of conditions would be LEAST likely to result in ideal gas behavior? A. High pressure and low temperature B. Low temperature and large volume C. High pressure and large volume D. Low pressure and high temperature

A. High pressure and low temperature - Gases deviate from ideal behavior at high pressures and lower volumes and temperatures, all of which force molecules closer together. The closer they are, the more they can participate in intermolecular forces, which violates the definition of an ideal gas. At low temperatures, the kinetic energy of the particles is reduced, so collisions with other particles or the walls of the container are more likely to result in significant changes in kinetic energy

A certain chemical reaction has the following rate law: Rate = k[NO2][Br2] Which of the following statements necessarily describe(s) the kinetics of this reaction? I. The reaction is second-order II. The amount of NO2 consumed is equal to the amount of Br2 consumed III. The rate will not be affected by the addition of a compound other than NO2 and Br2 A. I only B. I and II only C. II and III only D. I, II, and III

A. I only - If the sum of the exponents (orders) of the concentrations of each species in the rate law is equal to 2, then the reaction is second order. The exponents in the rate law are unrelated to stoichiometric coefficients, so NO2 and Br2 could have any stoichiometric coefficients in the original reaction and still be a second-order reaction, invalidating statement II. Statement III is incorrect because the rate can be affected by a wide variety of compounds.

If a reaction has a Keq less than Q, what is true about this reaction? A. Reactant formation will be favored B. Heat is a product C. The reaction is endergonic under standard conditions D. The reaction is exergonic under standard conditions

A. Reactant formation will be favored - When Keq is less than Q (Q > K), there will be more reactants than products at equilibrium. When Keq is more than Q (Q < K), there will be more products than reactants at equilibrium. Therefore, since Keq is given to be less then Q, reactant formation will be favored.

Carbonated beverages are produced by dissolving carbon dioxide in water to produce carbonic acid: CO2(g) + H2O(l) ↔ H2CO3 (aq) When a bottle containing carbonated water is opened, the taste of the beverage gradually changes as the carbonation is lost. Which of the following statements best explains this phenomenon? A. The change in pressure and volume causes the reaction to shift to the left, thereby decreasing the amount of aqueous carbonic acid B. The change in pressure and volume causes the reaction to shift to the right, thereby decreasing the amount of gaseous carbon dioxide C. Carbonic acid reacts with environmental oxygen and nitrogen D. Carbon dioxide reacts with environmental oxygen and nitrogen

A. The change in pressure and volume causes the reaction to shift to the left, thereby decreasing the amount of aqueous carbonic acid - Carbon dioxide gas evolves and leaves the bottle, which decreases the total pressure of the reactants. Le Chatelier's Principle explains that a decrease in pressure shifts the equilibrium to increase the number of moles of gas present. This particular reaction will shift to the left, which in turn will decrease the amount of carbonic acid and increase the amount of carbon dioxide and water.

For a cell with the following half-reactions: Anode: SO2 + 2 H2O -------> SO4^2- + 4H+ + 2e Cathode: Pd^2+ + 2e --------> Pd How would decreasing the pH of the solution inside the cell affect the electromotive force (emf)? A. The emf would decrease B. The emf would remain the same C. The emf would increase D. The emf would become zero

A. The emf would increase - A change in pH has a direct correlation to the hydrogen ion (H+) concentration. Decreasing the pH increases the H+ concentration, which means the concentration of products has increased in the oxidation of sulfur dioxide. This means it would be harder to liberate electrons, thus decreasing the emf. One could also view this decrease in oxidation potential as an increase in reduction potential. If E°red,anode increases, then E°cell must decrease according to E°cell = E°red,cathode - E°red,anode.

If Kc >> 1: A. The equilibrium mixture will favor products over reactants B. The equilibrium mixture will favor reactants over products. C. The equilibrium concentrations of reactants and products are equal. D. Th reaction is essentially irreversible

A. The equilibrium mixture will favor products over reactants - The larger the value of Keq (whether Kc or Kp), the larger the ratio of products to reactants. Therefore, if Kc >> 1, there are significantly larger concentrations of products than reactants at equilibrium. Even with a larger Keq, the reaction will ultimately reach equilibrium far toward the products side and is therefore reversilbe, eliminating (D).

Which of the following statements best describes the effect of lowering the temperature of the following reaction? A + B ↔ C + D ΔH = -1.12 kJ/mol A. [C] and [D] would increase B. [A] and [B] would increase C. ΔH would increase D. ΔH would decrease

A. [C] and [D] would increase - A negative ΔH value indicates an exothermic reaction, meaning that the forward reaction produces heat. Visualize this as follows: A + B ↔ C + D + heat This means that removing heat by decreasing the temperature is similar to removing any other product of the reaction. To compensate for this loss, the reaction will shift to the right, causing an increase in the concentrations of C and D, as well as a decrease in the concentrations of A and B.

The kinetic molecular theory states that: A. the average kinetic energy of a molecule of gas is directly proportional to the temperature of the gas in kelvins B. collisions between gas molecules are inelastic C. gas particles occupy discrete areas of space D. all gas molecules have the same kinetic energy at the same temperature

A. the average kinetic energy of a molecule of gas is directly proportional to the temperature of the gas in kelvins - The average kinetic energy is directly proportional to the temperature of a gas in kelvins. The kinetic molecular theory states that collisions between molecules are elastic and thus do not result in a loss of energy, eliminating (B). Gas particles are assumed to take up negligible space in kinetic molecular theory, eliminating (C). While the average kinetic energy of a gas as a whole is the same at a given temperature, the particles themselves have a distribution of speeds (as seen in the Maxwell-Boltzmann distribution curve), eliminating (D).

Explosions are necessarily characterized by: A. ΔG < 0 B. ΔH > 0 C. ΔS < 0 D. T < 0

A. ΔG < 0 - In an explosion, a significant amount of heat energy is released, meaning that the reaction is exothermic (ΔH < 0), eliminating (B). The entropy change associated with an explosion is positive because energy is dispersed over a much larger area, eliminating (C). If this is true, the expression ΔH- TΔS must be negative, indicating that this is an exergonic process (ΔG < 0). Absolute temperature can never be negative, eliminating (B).

The salt KCl is dissolved in a beaker. To an observer holding the beaker, the solution begins to feel colder as the KCl dissolves. From this observation, one could conclude that: A. ΔSsol'n is large enough to overcome the unfavorable ΔHsol'n B. KCl is mostly insoluble in water C. ΔSsol'n must be negative when KCl dissolves D. boiling point depression will occur in this solution

A. ΔSsol'n is large enough to overcome the unfavorable ΔHsol'n - Dissolution is governed by enthalpy and entropy, which are related by the equation ΔGsol'n = ΔHsol'n - TΔSol'n. The cooling of the solution indicates that heat is used up in this bond-breaking reaction. In other words, dissolution is endothermic, aka ΔH = positive. The reaction is occurring spontaneously, so ΔG must be negative. The only way that a positive ΔH can result in a negative ΔG is if entropy, ΔS, is a large, positive value as in (A). Conceptually, that means that the only way the solid can dissolve is if the increase in entropy is great enough to overcome the increase in enthalpy. (B) is incorrect because it is clearly stated in the question stem that KCl dissolves; further, all salts of Group 1 metals are soluble. (C) is incorrect because ΔSsol'n must be positive in order for KCl to dissolve. Finally, (D) is incorrect because solute dissolution would cause the boiling point to elevate, not depress. It is also not a piece of evidence that could be found simply be observing the beaker's temperature change.

Which of the following will cause the greatest increase in the boiling point of water when it is dissolved in 1.0kg H2O? A. 0.4 mol calcium sulfate B. 0.5 mol iron (III) sulfate C. 1.0 mol acetic acid D. 1.0 mol sucrose

B. 0.5 mol iron (III) sulfate - The equation to determine the change in boiling point of a solution is as follows ΔTb = (i)(Kb)(m). m is the molality of the solution and Kb is the boiling point elevation constant. In this case, the solvent is always water, so Kb will be the same for each solution. What is needed is the number of dissociated particles from each of the original species. This is referred to as the van't Hoff factor (i) and is multiplied by molality to give a normality (the concentration of the species of interest--in this case, all particles). The normality values determine which species can cause the greatest change in boiling point.

Which of the following equations describes the maximum number of electrons that can fill a subshell? A. 2l + 2 B. 4l + 2 C. 2l^2 D. 2l^2 + 2

B. 4l + 2 - This formula describes the number of electrons in terms of the azimuthal (angular momentum) quantum number, l, which ranges from 0 to n-1, with n being the principle quantum number. A table of the maximum number of electrons per subshell is provided here:

Suppose an electron falls from n=4 to its ground state, n=1. which of the following effects is most likely to happen? A. A photon is absorbed B. A photon is emitted C. The electron moves into a p-orbital D. The electron moves into a d-orbital

B. A photon is emitted - Because the electron is moving into the n=1 shell, the only subshell available is the 1s subshell, which eliminates (C) and (D). There will be some energy change, however, as the electron must lose energy to return to the minimum-energy ground state. That will require emitting radiation in the form of a photon. If the electron were to move from the ground state to an excited state, it will need to absorb energy instead.

Which of the following actions does NOT affect the equilibrium position of a reaction? A. Adding or removing heat B. Adding or removing a catalyst C. Increasing or decreasing concentrations of reactants D. Increasing or decreasing volumes of reactants

B. Adding or removing a catalyst - The equilibrium of a reaction can be changed by several factors. Adding or subtracting heat, (A), would shift the equilibrium based on the enthalpy change of the reaction. Increasing reactant concentrations would shift the equilibrium in the opposite direction of the product, and the opposite would occur if reactant concentrations were decreased, eliminating (C). Changing the volume of a reactant would affect any reaction with gaseous reactants or products, eliminating (D). While adding or removing a catalyst would change the reaction rates, it would not change where the equilibrium lies.

Which of the following electronic transitions would result in the greatest gain in energy for a single hydrogen electron? A. An electron moves from n=6 to n=2 B. An electron moves from n=2 to n=6 C. An electron moves from n=3 to n=4 D. An electron moves from n=4 to n=3

B. An electron moves from n=2 to n=6 - For the electron to GAIN energy, it must ABSORB energy from photons to jump up to a higher energy level. There is a bigger jump between n=2 to n=6 than there is between n=3 to n=4.

Which of the following would make the strongest electrolytic solution? A. A nonpolar covalent compound with significant solubility B. An ionic compound composed of one cation with a +3 charge and 3 anions with -1 charge C. A polar covalent compound with a small dissociation constant D. An ionic compound composed of two cations with +1 charge and one anion with -2 charge

B. An ionic compound composed of one cation with a +3 charge and 3 anions with -1 charge - The best electrolytes dissociate readily (have a high dissociation constant) and are ionic compounds with large amounts of cations and anions. This rules out (A) and (C). (D) has fewer total ions with a smaller total magnitude of charge and therefore is not as strong as an electrolyte as (B).

When dissolved in water, which of the following ions is most likely to form a complex ion with H2O (water)? A. Na+ B. Fe2+ C. Cl- D. S2-

B. Fe2+ - Iron is a transition metal. Transition metals can often form more than one ion. Iron, for example, can be Fe2+ or Fe3+. The transition metals, in these various oxidation states, can often form hydrogen complexes with water. Part of the significance of these complexes is that, when a transition metal can form a complex, its solubility within the related solvent will increase. The other ions given might dissolve readily in water, but because none of them are transition metals, they will likely not form complexes.

Consider the reaction: H2O(l) + CO2(aq) ↔ H2CO3(aq). If the concentration of carbon dioxide is doubled, then the reaction quotient will: A. Double B. Halve C. Stay the same D. Quadruple

B. Halve - While Keq is the equilibrium ratio of products to reactants under standard state conditions, and is independent of the concentrations of products or reactants, Q (reaction quotient) is the ratio of products to reactants at a given point in time. Q is not a constant, while Keq is. Doubling the number of reactants will therefore halve the reaction quotient of this reaction.

The gaseous state of matter is characterized by which of the following properties? I. Gases are compressible II. Gases assume the volume of their containers III. Gas particles exist as diatomic molecules A. I only B. I and II only C. II and III only D. I, II, and III

B. I and II only - Gases are easily compressible because they travel freely with large amounts of space between molecules. Because gas particles are far apart from each other and in rapid motion, they tend to take up the volume of their container. Many gases exist as diatomic molecules, but this is not a property that characterizes all gases, eliminating option III.

Which of the following species is represented by the electron configuration 1s2 2s2 2p6 3s2 3p6 4s1 3d5? I. Cr II. Mn+ III. Fe2+ A. I only B. I and II only C. II and III only D. I, II, and III

B. I and II only - When dealing with ions, you cannot directly approach electronic configuration based on the number of electrons they currently hold. First examine the neutral atom's configuration, and then determine which electrons are removed: Due to the stability if half-filled d-orbitals, neutral chromium assumes the electron configuration of [Ar] 4s1 3d5. Mn must lose one electron from its initial configuration to become the Mn+ cation. That electron would come from the 4s subshell according to the rule that the first electron removed comes from the highest-energy shell. Fe must lose 2 electrons to become the Fe2+ cation. They'll both be lost from the same orbital; the only way Fe2+ could hold the configuration in the question stem would be if one d-electron and one s-electron were lost together; and that cannot happen.

Which of the following is true of equilibrium reactions? I. An increase in k1 results in a decrease in k-1 II. As the concentrations of products increases, the concentrations of reactants decreases III. The equilibrium constant is altered by changes in temperature A. I only B. II and III only C. I and III only D. I, II, and III

B. II and III only - Statement I is false because the addition of a catalyst could increase the rate constants of both the forward and reverse reactions. Statement II is true because--for products to come into existence--reactants must be used up. Statement III is also true: all K values are temperature-dependent.

A resonance structure describes: I. the hybrid of all possible structures that contribute to electronic distribution II. a potential arrangement of electrons in a molecule III. the single form that the molecule most often takes A. I only B. II only C. I and II only D. I, II, and III

B. II only - A resonance structure describes an arrangement of electrons in a molecule. Different resonance structures can be derived by moving electrons in unhybridized p-orbitals throughout a molecule containing conjugated bonds. In molecule that contain multiple resonance structures, some are usually more stable than others; however, each resonance structure is not necessarily the most common form a molecule takes, eliminating statement III. Statement I has reversed the terminology for resonance structures: the electron density in a molecule is the weighted average of all possible resonance structures, not the other way around.

Why is a single bond stronger than a π bond? I. π bonds have greater orbital overlap II. s-orbitals have more overlap than p-orbitals III. sp3 hybridization is always unstable A. I only B. II only C. I and III only D. II and III only

B. II only - Bond strength is determined by the degree of orbital overlap; the greater the overlap, the greater the bond strength. A π bond is weaker than a single bond because there is significantly less overlap between the unhybridized p-orbitals of a π bond (due to their parallel orientation) than between the s-orbitals or hybrid orbitals of a σ bond. Sp3-hybridized orbitals can be quite stable, as evidenced by the number of carbon atoms with this hybridization forming stable compounds.

Ideal gases: I. have no volume II. have particles with no attractive forces between them III. have no mass A. I only B. II only C. I and II only D. I, II, and III

B. II only - Ideal gases are said to have no attractive forces between molecules. While each particle within the gas is considered to have negligible volume, ideal gases as a whole certainly do have a measurable volume, thus option I is eliminated. Gases have molar masses, thus option III is eliminated.

If the surface area of an electrode material in an electrochemical cell is tripled, what else is necessarily tripled? I. E°cell II. Current III. Keq A. I only B. II only C. I and II only D. II and III only

B. II only - Potential, as measured by E°cell, is dependent only on the identity of the electrodes and not the amount present. Similarly, the equilibrium constant depends only on the identity of the electrolyte solutions and the temperature. However, as the electrode material is increased, the surface area participating in oxidation-reduction reactions is increased and more electrons are released, making statement II correct.

Acetic acid dissociates in solution according to the following equation; CHCOOH ↔ CH3COO- + H+ If sodium acetate, is added to a solution of acetic acid in excess water, which of the following effects would be observed in the solution? A. Decreased pH B. Increased pH C. Decreased pKeq (pKa) D. Increased pKeq (pKa)

B. Increased pH - Adding sodium acetate (NaCH3COO) increases the number of acetate ions (CH3COO-) present. According to Le Chatelier's Principle, this change will push the reaction to the left, decreasing the number of H+ ions. Because pH is determined by the hydrogen ion concentration, a decrease in the number of free protons will increase the pH. An acid's Ka (which is simply the Keq for acid dissociation) will remain constant under a given temperature and pressure, eliminating (C).

What is the most specific characterization of the reaction shown? Ca(OH)2(aq) + H2SO4(aq) ↔ CaSO4(aq) + H2O(l) A. Single-displacement B. Neutralization C. Double-displacement D. Oxidation-reduction

B. Neutralization - This reaction is a classic example of a neutralization reaction, in which an acid and a base react to form a salt and, usually, water. Although this reaction also fits the criteria for a double-displacement reaction, (C), in which two molecules essentially exchange ions with ech other, neutralization is a more specific description of the process.

Which of the following compounds is LEAST likely to be found in the salt bridge of a galvanic cell? A. NaCl B. SO3 C. MgSO3 D. NH3NO3

B. SO3 - Salt bridges contain inert electrolytes. Ionic compounds such as (A), (C), and (D), are known to be strong electrolytes because they completely dissociate in solution. (B) cannot be considered an electrolyte because its atoms are covalently bonded and will not dissociate in aqueous solution. (B) and (C) may appear similar, but there is an important distinction to be made. (C) implies that Mg^2+ and SO3^2-are the final, dissociated ionic constituents, while (B) implies that the neutral SO3 would have to be dissolved in solution.

When ammonia, NH3, is used as a solvent, it can form complex ions. For example, dissolving AgCl in NH3 will result in the complex ion [Ag(NH3)]^2+. What effect would the formation of complex ions have on the solubility of a compound like AgCl in NH3? A. The solubility of AgCl will increase because complex ion formation will cause more ions to exist in solution, which interact with AgCl to cause it to dissociate B. The solubility of AgCl will increase because complex ion formation will consume Ag+ ions and cause the equilibrium to shift away from solid AgCl C. The solubility of AgCl will decrease because Ag+ ions are in complexes, and the Ag+ ions that are not complexed will associate with Cl- to form solid AgCl D. The solubility of AgCl will decrease because complex ion formation will consume Ag+ ions and cause the equilibrium to shift toward the solid AgCl

B. The solubility of AgCl will increase because complex ion formation will consume Ag+ ions and cause the equilibrium to shift away from solid AgCl - Formation of complex ions between silver ions and ammonia will cause more molecules of solid AgCl to dissociate. The equilibrium is driven toward dissociation because the Ag+ ions are essentially being removed from solution when they complex with ammonia. This rationale is based upon Le Chatelier's Principle, stating that when a chemical experiences a change in concentration, the system will shift to counteract that change.

If a certain metal has multiple oxidation states, its acidity as an oxide generally increases as the oxidation state increases. Therefore, which of the following tungsten compounds is likely to be the strongest acid? A. WO2 B. WO3 C. W2O3 D. W2O5

B. WO3 - Recall that oxygen has an oxidation state of -2. Therefore, in tungsten (IV) oxide, (A), tungsten has an oxidation state of +4. In tungsten (VI) oxide, (B), it has an oxidation state of +6. In tungsten (III) oxide, (C), it is +3. In tungsten pentoxide, (D), it is +5.

A reaction that utilizes oxygen and hydrocarbons as reactants and that produces carbon dioxide and water as products is best characterized as: A. single-displacement B. combustion C. metathesis D. decomposition

B. combustion - This description characterizes a combustion reaction because a hydrocarbon acts as a fuel when reacting with oxygen. Carbon dioxide (an oxide) and water are the products of such a reaction.

A carbon atom participates in one double bond. As such this carbon contains orbitals with: A. hybridization between the s- orbital and one p-orbital B. hybridization between the s- orbital and two p- orbitals C. hybridization between the s- orbital and three p- orbitals D. unhybridized s character

B. hybridization between the s- orbital and two p- orbitals - In a carbon with one double bond, sp2 hybridization occurs, that is, one s-orbital hybridizes with two p-orbitals to form three sp2-hybridized orbitals. The third orbital of the carbon atom remains unhybridized and takes part in the formation of the π bond of the double bond. Although there is an unhybridized p-orbital, there are no unhybridized s-orbitals, eliminating (D).

Molecular orbitals contain a maximum of: A. one electron B. two electrons C. four electrons D. 2n^2 electrons, where n is the principle quantum number of the combining atomic orbitals

B. two electrons - Like atomic orbitals, molecular orbitals each can contain a maximum of two electrons with opposite signs. The 2n^2 rule in (D) refers to the total number of electrons that can exist in a given energy shell, not in a molecular orbital.

What is the oxidation number of Chlorine in NaClO? A. -1 B. 0 C. +1 D. +2

C. +1 - In NaClO4 (sodium hypochlorite), sodium carries its typical +1 charge, and oxygen carries its typical -2 charge. This means that the chlorine atom must carry a +1 charge in order to balance the overall charge of zero

Consider the following two reactions: 3 A + 2 B ↔ 3 C + 4 D (Reaction 1) 4 D + 3 C ↔ 3 A + 2 B (Reaction 2) If Keq for reaction 1 is equal to 0.1, what is Keq for reaction 2? A. 0.1 B. 1 C. 10 D. 100

C. 10 - Reaction 2 is the reverse of reaction 1. This means that Keq for reaction 2 is the inverse of Keq of reaction 1, so the answer is 1/0.1 = 10.

What is the maximum number of electrons allowed in a single atomic energy level in terms of the principal quantum number, n? A. 2n B. 2n + 2 C. 2n^2 D. 2n^2 + 2

C. 2n^2 - For any value of n, there will be a maximum number of 2n^2 electrons; that is, two per orbital. This can also be determined from the periodic table. There are only two elements (H & He) that have valence electrons in the n=1 shell. Eight elements (Li to Ne) have valence electrons in the n=2 shell. This is the only equation that matches this pattern

Although the octet rule dictates much of molecular structure, some atoms can violate the octet rule by being surrounded by more than eight electrons. Which of the following is the best explanation for why some atoms can exceed the octet? A. Atoms that exceed the octet already have eight electrons in their outermost electron shell B. Atoms that exceed the octet only do so when bonding with transition metals C. Atoms that exceed the octet can do so because they have d-orbitals in which extra electrons can reside D. Some atoms exceed the octet because they are highly electronegative

C. Atoms that exceed the octet can do so because they have d-orbitals in which extra electrons can reside - All atoms in the third period (row) of the periodic table have d-orbitals, which can hold an additional 10 electrons. The typical "octet" electrons reside in s- and p-orbitals, but elements in period 3 or higher can place electrons into these d-orbitals.

The entropy change when a solution forms can be expressed by the term ΔSsol'n. When water molecules become ordered around an ion as it dissolves, the ordering would be expected to make a negative contribution to ΔSsol'n. An ion that has more charge density will have a greater hydration effect, or ordering of water molecules. Based on this information, which of the following compounds will have the most negative contribution to ΔSsol'n? A. KCl B. LiF C. CaS D. NaCl

C. CaS - CaS will cause the most negative contribution to ΔSsol'n through hydration effects because Ca2+ and S2- ions have the highest charge density compared to the other ions. All of the other ions have charges of +1 or -1, whereas Ca2+ and S2- each have charges with a magnitude of 2.

Which of the following changes is associated with the largest decrease in entropy? A. Fusion B. Solidification C. Deposition D. Sublimation

C. Deposition -Gases have the highest entropy, and solids have the lowest. Therefore, a phase change from a gas to a solid--deposition--would have the largest decrease in entropy of any phase change process.

Which of the following types of intermolecular forces provides the most accurate explanation for why noble gases can liquify? A. Hydrogen bonding B. Ion-dipole interactions C. Dispersion forces D. Dipole-dipole interactions

C. Dispersion forces - All of the listed types of forces describe interactions between different types of molecules. However, noble gases are entirely uncharged and do not have polar covalent bonds, ionic bonds, or dipole moments. Therefore, the only intermolecular forces experienced by noble gases are London dispersion forces. Although these interactions are small in magnitude, they are necessary for condensation into a liquid.

Experimenters notice that the molar concentration of dissolved oxygen in an enclosed water tank has decreased to one-half its original value. In an attempt to counter this decrease, they quadruple the partial pressure of oxygen in the container. What is the final concentration of the gas? A. Half of the original concentration B. The same as the original concentration C. Double the original concentration D. Quadruple the original concentration

C. Double the original concentration - Initially the concentration of the gas is decreased to one-half its original value. Recall that concentration (solubility) and partial pressure are directly related--as one increases, the other increases. If the experimenters then quadruple the partial pressure of oxygen in the vessel, the solubility is also increased by a factor of 4. One-half times four gives twice the original concentration value. Misreading the answer choices as being related to the concentration before the experimenters increased the partial pressure leads to (D).

Which of the following is the best explanation of the phenomenon of hydrogen bonding? A. Hydrogen has a strong affinity for holding onto valence electrons B. Hydrogen can hold only two valence electrons C. Electronegative atoms disproportionately carry shared electron pairs when bonded to hydrogen D. Hydrogen bonds have ionic character

C. Electronegative atoms disproportionately carry shared electron pairs when bonded to hydrogen - Electronegative atoms bonded to hydrogen disproportionately pull covalently bonded electrons toward themselves, which leaves hydrogen with a partial positive charge. That partial positive charge is attracted to nearby negative or partial negative charges, such as those on other electronegative atoms.

Which of the following best describes the number and character of bonds in an ammonium cation? A. Three polar covalent bonds B. Four polar covalent bonds, of which none are coordinate covalent bonds C. Four polar covalent bonds, of which one is a coordinate covalent bond D. Four polar covalent bonds, of which two are coordinate covalent bonds

C. Four polar covalent bonds, of which one is a coordinate covalent bond - First recall that ammonium is NH4+ while ammonia is NH3. Ammonium is formed by the association of NH3, an uncharged molecule with a lone pair on the central nitrogen atom, with a positively charged hydrogen cation with no electrons or lone pairs. In other words, NH3 is a Lewis Base (electron donor), while H+ is a Lewis Acid (electron acceptor). This type of bonding between a Lewis Acid and Lewis Base us a coordinate covalent bond.

Consider the following equation: 6 Na(s) + 2 NH3(aq) ----> 2 Na3N(s) + 3 H2(g) Which species acts as an oxidizing agent? A. Na B. N in NH3 C. H in NH3 D. H2

C. H in NH3 - The oxidizing agent is the species that is reduced in any given equation. In this problem, six hydrogen atoms with +1 oxidation states in NH3 are reduced to three neutral H2 molecules.

What determines the length of an element's atomic radius? I. The number of valence electrons II. The number of electron shells III. The number of neutrons in the nucleus A. I only B. II only C. I and II only D. I, II, and III

C. I and II only - Atomic radius is determined by multiple factors. Of the choices given, the number of valence electrons DOES have an impact on the atomic radius. As one moves across a period (row), protons and valence electrons are added, and the electrons are more strongly attracted to the central protons. This attraction tightens the atom, shrinking the atomic radius. The number of electron shells is also significant, as demonstrated by the trend when moving down a group (column). As more electron shells are added that separate the positively charged nucleus from the outermost electrons, the electrostatic forces are weakened, and the atomic radius increases. The number of neutrons is irrelevant because it does not impact these attractive forces.

Which of the following structures contribute(s) most to Nitric Oxide's (NO2) resonance hybrid? I. O---N===O II. O===N---O III. O---N---O A. I only B. III only C. I and II only D. I, II, and III only

C. I and II only - The two greatest contributors are structures I and II. Resonance structures are representations of how charges are shared across a molecule. In reality, the charge distribution is a weighted average of contributing resonance structures. The most stable resonance structures are those that minimize charge on the atoms in a molecule; the more stable the structure, the more it will contribute to the overall charge distribution in the molecule. Structures I and II minimize formal charges, so it will be the largest contributors to the resonance hybrid.

An electrolytic cell is filled with water. Which of the following will move towards the cathode of such a cell? I. H+ ions II. O^2- ions III. Electrons A. I only B. II only C. I and III only D. II and III only

C. I and III only - In an electrolytic cell, ionic compounds are broken up into their constituents; the cations (positively charged ions) migrate toward the cathode, and the anions (negatively charged ions) migrate toward the anode. In this case, the cations are H+ ions (protons), so option I is correct. Electrons flow from anode to cathode in all types of cells, meaning that option III is also correct. Option II is incorrect for two reasons. First, it is unlikely that the anions in any cell would be O^2- rather than OH-. Second, and more significantly, these anions would flow to the anode, not the cathode.

Rusting occurs due to the oxidation-reduction reaction of iron with environmental oxygen: 4 Fe(s) + 3 O2(g) ------------------> 2 Fe2O3(s) Some metals cannot react with oxygen in this fashion. Which of the following best explains why iron can't? A. Iron has a more positive reduction potential than those metals, making it more likely to donate electrons to oxygen B. Iron has a more positive reduction potential than those metals, making it more likely to accept electrons from oxygen C. Iron has a less positive reduction potential than those metals, making it more likely to donate electrons to oxygen D. Iron has a less positive reduction potential than those metals, making it more likely to accept electrons from oxygen

C. Iron has a less positive reduction potential than those metals, making it more likely to donate electrons to oxygen - In the oxidation-reduction reaction of a metal with oxygen, the metal will be oxidized (donate electrons) and oxygen will be reduced (accept electrons). This fact allows us to immediately eliminate (B) and (D). A species with a higher reduction potential is more likely to be reduced, and a species with a lower reduction potential is more likely to be oxidized. Based on the information in the question, iron is oxidized more readily than those metals; this means that iron has a lower reduction potential.

An electrolytic cell necessarily has: A. ΔS° > 0 B. ΔG° < 0 C. Keq < 1 D. E°cell > 0

C. Keq < 1 - An electrolytic cell is nonspontaneous. Therefore, the ΔG° must be positive and the emf (E°cell) must be negative, eliminating (B) and (D). The change in entropy may be positive or negative, depending on the species involved, eliminating (A). According to the equation ΔG° = -RT lnKeq, Keq < 1 would result in lnKeq < 0, which means ΔG° > 0.

Which of the following explanations best describes the mechanism by which solute particles affect the melting point of ice? A. Melting point is elevated because the kinetic energy of the substance increases B. Melting point is elevated because the kinetic energy of the substance decreases C. Melting point is depressed because solute particles interfere with lattice formation D. Melting point is depressed because solute particles enhance lattice formation

C. Melting point is depressed because solute particles interfere with lattice formation - Melting point depresses upon solute addition, making (A) and (B) incorrect. Solute particles interfere with lattice formation, the highly organized state in which solid molecules align themselves. Colder-than-normal conditions are necessary to create the solid structure

Metals are often used for making wires that conduct electricity. Which of the following properties of metals explains why? A. Metals are malleable B. Metals have low electronegativities C. Metals have valence electrons that can move freely D. Metals have high melting points

C. Metals have valence electrons that can move freely - All four descriptions of metals are true, but the most significant property that contributes to the ability of metals to conduct electricity is the fact that they have valence electrons that can move freely. Malleability, (A), is the ability to shape a material with a hammer, which does not play a role in conducting electricity. The low electronegativity and high melting point of metals, (B) and (D), also do not play a major role in the conduction of electricity.

Compound A has a higher Ka (equilibrium constant of acid dissociation) of approximately 10^-4. Which of the following compounds is most likely to react with a solution of compound A? A. HNO3 B. NO2 C. NH3 D. N2O5

C. NH3 - Ka is equal to the ration of products to reactants, with each species raised to its stoichiometric coefficient. A compound with a Ka greater than 10^-7 contains more H+ cations than HA- anions at equilibrium, which makes it an acid. This means that the compound in question is likely to react with a compound that is basic Of the four answer choices, NH3 is the only base.

Consider the reaction: H2O(l) + CO2(aq) ↔ H2CO3(aq). If the concentrations of any one of the reactants is doubled, then the equilibrium constant will: A. Double B. Halve C. Stay the same D. Quadruple

C. Stay the same - Keq is the equilibrium ratio of products to reactants under standard state conditions, and is INDEPENDENT of the concentration of products or reactants.

If this reaction were exothermic, what effect would decreasing the temperature have on the equilibrium? FeI(aq) + I2(g) ↔ FeI3(aq) A. The forward reaction rate and the reverse reaction rate both increase B. The forward reaction rate decreases while the reverse reaction rate increases C. The forward reaction rate increases while the reverse reaction rate decreases D. The forward reaction rate and the reverse reaction rate both decrease

C. The forward reaction rate increases while the reverse reaction rate decreases - An exothermic reaction produces heat. Decreasing the temperature favors product formation, resulting in an increase in the forward reaction rate with a concomitant decrease in the reverse reaction rate.

In which of the following situations is it impossible to predict how the pressure will change for a gas sample? A. The gas is cooled at a constant volume B. The gas is heated at a constant volume C. The gas is heated, and the volume is simultaneously increased D. The gas is cooled, and the volume is simultaneously increased

C. The gas is heated, and the volume is simultaneously increased - Both a change in temperature and a change in volume can affect a gas's pressure. So if one of those two variables is kept constant, as in (A) and (B), we'll definitely be able to predict which way the pressure will change. At a constant volume, heating a gas will increase its pressure, and cooling the gas will decrease it. What about when both temperature and volume are changing? If both changes have the same effect on pressure, then we can still predict which way it will change. This is the case in (D). Cooling the gas and increasing its volume both decrease pressure. (C), on the other hand, presents too vague a scenario for us to predict definitely the change in pressure. Heating the gas would amplify the pressure, while increasing the volume would decrease it. Without knowing the magnitude of each influence, it's impossible to say whether the pressure would increase, decrease, or stay the same.

What is the highest-energy orbital of elements with valence electrons in the n=3 shell? A. s-orbital B. p-orbital C. d-orbital D. f-orbital

C. d-orbital - When n=3, l=0, 1, or 2. The highest value for l in this case is 2, which corresponds to the d subshell. Although the 3d block appears to be part of the fourth period (row), it still has the principal quantum number n=3. In general, the subshells within an energy shell increase in energy as follows: s < p < d < f (although there is no 3f subshell).

Which of the following statements is true of a process that is spontaneous in the forward direction? A. ΔG > 0 and Keq > Q B. ΔG > 0 and Keq < Q C. ΔG < 0 and Keq > Q D. ΔG < 0 and Keq < Q

C. ΔG < 0 and Keq > Q - For a process to progress forward spontaneously, Q must be less than Keq and will therefore have a tendency to move in the direction toward equilibrium. A spontaneous reaction's free energy is negative by convention.

At standard temperature and pressure, a chemical process is at equilibrium. what is the free energy of reaction (ΔG) for this process? A. ΔG > 0 B. ΔG < 0 C. ΔG = 0 D. There is not enough information to determine the free energy of the reaction

C. ΔG = 0 - Standard temperature and pressure indicate 0℃ and 1 atm. Gibbs free energy is temperature dependent, but if a reaction is at equilibrium, ΔG = 0.

The following electronic configurations represent elements in their neutral form. Which element is the strongest oxidizing agent? A. 1s2 2s2 2p6 3s2 3p6 4s2 B. 1s2 2s2 2p6 3s2 3p6 4s2 3d5 C. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p1 D. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

D. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 - A strong oxidizing agent will be easily reduced, meaning that it will have a tendency to gain electrons. Atoms usually gain electrons if they are one or two electrons away from filling up their valence shell. (A) has a full 4s-orbital, meaning that it can only gain an electron if it gains an entire sub-shell. (B) has a stable, half-full 3d-orbital, so it is unlikely to pick up electrons unless it can gain five. (C) has only a single electron in the outer shell, which is more likely lost upon ionization. (D) would fill up its 4p-orbital by gaining one electron, so it is easily reduced.

A saturated solution of cobalt (III) hydroxide (Ksp = 1.6 x 10^44) is added to a saturated solution of thallium (III) hydroxide (Ksp = 6.3 x 10^-46). What is likely to occur? A. Both cobalt (III) hydroxide and thallium (III) hydroxide remain stable in solution B. Cobalt (III) hydroxide precipitates and thallium (III) hydroxide remains stable in solution C. Thallium (III) hydroxide precipitates and cobalt (III) hydroxide remains stable in solution D. Both thallium (III) hydroxide and cobalt (III) hydroxide precipitate

D. Both thallium (III) hydroxide and cobalt (III) hydroxide precipitate - Since both salts have a formula MX3 (one of one particle, three of another), it is possible to directly compare the molar solubilites of each. When the solutions are mixed, [OH-] is above saturation levels for both the cobalt and the thallium in the solution. Since thallium (III) hydroxide has a smaller Ksp than that of cobalt (III) hydroxide, it will react first. The ion product of the mixed solution is higher than the Ksp for thallium (III) hydroxide, and the system will shift left to precipitate solid thallium (III) hyrdoxide. After the thallium (III) hydroxide precipitates, a small excess of OH- will remain, which gives an ion product slightly above the Ksp of cobalt (III) hydroxide. This will cause a small amount (1-3%) of cobalt (III) hydroxide to also precipitate.

Which of the following processes has the most exothermic standard heat of combustion? A. Combustion of ethane B. Combustion of propane C. Combustion of n-butane D. Combustion of n-pentane

D. Combustion of n-pentane - Combustion often involves the reaction of a hydrocarbon with oxygen to produce carbon dioxide and water. Longer hydrocarbon chains yield greater amounts of combustion products and release more heat in the process--that is, there reaction is more exothermic. Of the hydrocarbons listed here, n-pentane is the longest chain.

The process of formation of a salt solution can be better understood into three steps: 1. Breaking the solute into its individual components 2. Making room for the solute in the solvent by overcoming intermolecular forces 3. Allowing solute-solvent interactions to occur to form the solution A. Endothermic, exothermic, endothermic B. Exothermic, endothermic, endothermic C. Exothermic, exothermic, endothermic D. Endothermic, endothermic, exothermic

D. Endothermic, endothermic, exothermic - The first step will most likely be endothermic because energy is required to break molecules apart. The second step is also endothermic because the intermolecular forces in the solvent must be overcome to allow incorporation of solute particles. The third step will most likely be exothermic because polar water molecules will interact with the dissolved ions, creating a stable solution and releasing energy.

If the value of E°cell is known, what other data is needed to calculate ΔG°? A. Equilibrium constant B. Reaction quotient C. Temperature of the system D. Half-reactions of the cells

D. Half-reactions of the cells - This answer comes directly from the equation relating Gibbs Free Energy and E°cell. ΔG° = -nFE°cell, where n is the number of moles of electrons transferred and F is the Faraday constant, 10^5 C in 1 mol of electrons. To determine n, one must look at the balanced half-reactions occurring in the oxidation-reduction reaction.

Which phases of solvent and solute can form a solution? I. Solid solvent, gaseous solute II. Solid solvent, solid solute III. Gaseous solvent, gaseous solute A. I and II only B. I and III only C. II and III only D. I, II, and III

D. I, II, and III - All three choices can make a solution as long as the two components create a mixture that is of uniform appearance (homogenous). Hydrogen in platinum is an example of a gas in a solid. Brass and steel are examples of homogenous mixtures of solids. The air we breathe is an example of a mixture of gases; while these are more commonly simply referred to as mixtures, they still fit the criteria of a solution.

Two atomic orbitals may combine to form: I. a bonding molecular orbital II. an anitbonding molecular orbital III. Hybridized orbitals A. I only B. III only C. I and II only D. I, II, and III

D. I, II, and III - When atomic orbitals combine, they form molecular orbitals. When two atomic orbitals with the same sign are added head-to-head, or tail-to-tail, they form bonding molecular orbitals. When two atomic orbitals with opposite signs are added head-to-head or tail-to-tail, they form antibonding molecular orbitals. Atomic orbitals can also hybridize, forming sp3, sp2, or sp orbitals.

Which of the following correctly ranks the compounds below by ascending boiling point? I. Acetone (C3H6O) II. KCl III. Kr IV. Isopropyl Alcohol A. I < II < IV < III B. III < IV < I < II C. II < IV < I < III D. III < I < IV < II

D. III < I < IV < II - The key to answering this question is to understand the types of intermolecular forces that exist in each of these molecules because larger intermolecular forces correspond to higher boiling points. Kr is a noble gas with a full octet, so the only intermolecular forces present are London dispersion forces. Acetone and isopropyl alcohol are both polar, so both have dipole-dipole interactions, which are stronger than dispersion forces. However, isopropyl alcohol contains hydrogen bonds, increasing its boiling point. Finally, the strongest interactions are ionic bonds, which exist in KCl.

A reactant in a second-order reaction at a certain temperature is increased by a factor of 4. By how much is the rate of the reaction altered? A. It is unchanged B. It is increased by a factor of 4 C. It is increased by a factor of 16 D. It cannot be determined from the information given

D. It cannot be determined from the information given - A second-order reaction can be second-order with respect go one reactant, or first-order with respect to two reactants. In this case, one reactant was increased by a factor of 4. If the reaction is second-order with respect to this reactant, the rate law will be rate=k[A]^2[B]^0 and the rate will increase by a factor of 16. If it is first-order with respect to this reactant and first-order with respect to another reactant, the rate law will be rate=k[A]^1[B]^1, and the rate will increase by a factor of 4. We do not know which of these is the correct rate law and, thus, cannot determine the effect on the rate.

Which of the following atoms or ions has the largest effective nuclear charge? A. Cl B. Cl- C. K D. K+

D. K+ - The effective nuclear charge refers to the strength with which the protons in the nucleus can pull on electrons. This phenomenon helps to explain electron affinity, electronegativity, and ionization energy. In (A), the non-ionized chlorine atom, the nuclear charge is balanced by the surrounding electrons: 17p+/17e-. The chloride ion, (B), has a lower effective nuclear charge because there are more electrons than protons: 17p+/18e-. Next, elemental potassium, (C), has the lowest effective nuclear charge because it contains additional inner shells that shield its valence electron from the nucleus. (D), ionic potassium, has a higher effective nuclear charge than any of the other options do because it has the same electron configuration as Cl- (and the same amount of shielding from inner shell electrons as neutral Cl) but contains two extra protons in its nucleus: 19pe-/18e-.

Which of the following choices is indicative of a spontaneous reaction, assuming standard conditions? A. E°cell is negative B. Q = Keq C. The cell is a concentration cell D. Keq > 1

D. Keq > 1 - A spontaneous electrochemical reaction has a negative ΔG. Using the equation ΔG° = -RT lnKeq, Keq > 1 would result in lnK > 0, which means ΔG° < 0. A negative electromotive force, (A), or equilibrium state, (B), would not correspond to a spontaneous reaction. Concentration cells can be spontaneous; however, if the concentration cell had reached equilibrium, it would cease to be a spontaneous reaction, eliminating (C). When an answer choice may be true, but does not HAVE TO be--it is the wrong answer on Test Day.

Pure sodium metal spontaneously combusts upon contact with room temperature water. What is true about the equilibrium constant of this combustion reaction at 25℃? A. Keq < 0 B. 0 < Keq < 1 C. Keq = 1 D. Keq > 1

D. Keq > 1 - Solve this question using the equation ΔG = -RTlnK. ΔGrxn is negative (as it must be for a spontaneous reaction), and R and T are always positive. Therefore, lnK must also be positive for the sign convention to work out correctly. Since ln(1) = 0, the natural logarithm of any number greater than 1 will be positive, and the natural logarithm for any number less than 1 will be negative. In order for lnK to be a positive number, Keq must be greater than 1.

A leak of helium gas through a small hole occurs at a rate of 3.22 x 10^-5 mol/s. How will the leakage rates of neon and oxygen gases compare to helium at the same temperature and pressure? A. Neon will leak faster than helium; oxygen will leak faster than helium B. Neon will leak faster than helium; oxygen will leak slower than helium C. Neon will leak slower than helium; oxygen will leak faster than helium D. Neon will leak slower than helium; oxygen will leak slower than helium

D. Neon will leak slower than helium; oxygen will leak slower than helium - Graham's law of effusion states that the relative rates of effusion of two gases at the same temperature and pressure are given by the inverse ratio of the square roots of the masses of the gas particles. In other words, a gas with a higher molar mass will leak more slowly than a gas with a lower molar mass. Both neon and oxygen gases will leak at slower rates than helium because they both have more mass than helium.

Despite the fact that both C2H2 and HCN contain triple bonds, the lengths of these triple bonds are not equal. Which of the following is the best explanation for this finding? A. In C2H2, the bond is shorter because it is between atoms of the same element B. The two molecules have different resonance structures C. Carbon is more electronegative than hydrogen D. Nitrogen is more electronegative than carbon

D. Nitrogen is more electronegative than carbon - Bond lengths decrease as the bond order increases, and they also increase with larger differences in electronegativity. In this case, because both C2H2 and HCN have triple bonds, we cannot compare the bond lengths based on bond order. We must then rely on periodic trends. The bond length decreases when moving to the right along the periodic table's rows because more electronegative atoms have shorter atomic radii. The nitrogen in HCN is likely to hold its electrons closer, or in a shorter radius, than the carbons in C2H2.

Which of the following experimental methods should NEVER affect the rate of a reaction? A. Placing an exothermic reaction in an ice bath B. Increasing the pressure of a reactant in a closed container C. Putting the reactants into an aqueous solution D. Removing the product of an irreversible reaction

D. Removing the product of an irreversible reaction - The question asks which alteration does NOT affect the rate of the reaction. Temperature directly affects the rate constant (k), making (A) incorrect. Changing the partial pressure of a gas will affect the number of effective collisions per time, which increase the reaction rate. This makes (B) incorrect— but note that concentration changes will not affect the rate of zero-order reactions. Solvents affect the rate of reactions depending on how the reactants interact with the solvent, making (C) incorrect. Removing the product of an irreversible reaction, (D), should not affect the rate of the reaction because the rate law does not depend on the concentration of products.

Why do halogens often form ionic bonds with alkaline earth metals? A. The alkaline earth metals have much higher electron affinities than the halogens B. By sharing electrons equally, the alkaline earth metals and halogens both form full octets C. Within the same row, the halogens have smaller atomic radii than the alkaline earth metals D. The halogens have much higher electron affinities than the alkaline earth metals

D. The halogens have much higher electron affinities than the alkaline earth metals - Ionic bonds are formed through unequal sharing of electrons. These bonds typically occur because the electron affinities of the two bonded atoms differ greatly. For example, the halogens have high electron affinities because adding a single electron to their valence shells would create full valence shells. In contrast, the alkaline earth metals have very low electron affinities and are more likely to be electron donors because the loss of two electrons would leave them with full valence shells. (A) states the opposite and is incorrect because the halogens have high electron affinity and the alkaline earth metals have low electron affinity.

What would increasing the concentration of reactants accomplish in a solution containing a saturated catalyst? A. It would increase the rate constant but not the reaction rate B. It would decrease the rate constant but increase the reaction rate C. It would increase the rate constant and increase the reaction rate D. The reaction rate would be unaffected

D. The reaction rate would be unaffected - While increasing the concentration can alter the reaction rate in first- or higher-order reactions, saturated solutions containing a catalyst have a maximum turnover rate and cannot increase the rate constant or the reaction rate any higher by adding more reactant molecules.

Which of the following can alter the emf of an electrochemical cell? A. The mass of the electrodes B. The length of the wire connecting the half-cells C. The overall size of the battery D. The temperature of the solution in the half-cells

D. The temperature of the solution in the half-cells - E°cell is dependent upon the change in free energy of the system (ΔG°) through the equation RT lnKeq = nFE°cell. The temperature (T) appears in this equation; thus, a change in temperature will impact the E°cell.

A reaction has a positive entropy and enthalpy. What can be inferred about the progress of this reaction from this information? A. The reaction is spontaneous B. The reaction is nonspontaneous C. The reaction is at equilibrium D. There is not enough information to determine whether the reaction is spontaneous or not

D. There is not enough information to determine whether the reaction is spontaneous or not - There is not enough information in the problem to determine whether or not the reaction is spontaneous. If the signs of enthalpy and entropy are the same, the reaction is temperature-dependent according to ΔG = ΔH - TΔS. Without the temperature, we cannot determine if this reaction is spontaneous, nonspontaneous, or at equilibrium.

In a certain equilibrium process, the activation energy of the forward reaction (Ea) is greater than the activation energy of the reverse reaction. This reaction is: A. endothermic B. exothermic C. spontaneous D. nonspontaneous

D. nonspontaneous - Before you try to answer this question, you should draw a free energy diagram for the system. If the activation energy of the forward reaction is greater than the activation energy of the reverse reaction, then the products must have a higher free energy than the reactants. The overall energy of the system is higher at the end than it was in the beginning. The net free energy change is positive (+), indicating an endergonic (nonspontaneous) reaction. The terms endothermic, (A), and exothermic, (B), are associated with enthalpy. While free energy does depend on enthalpy, it also depends on entropy; there is not enough information in the question stem to reliably determine the sign of the entropy change of the reaction.

The following system obeys second-order kinetics. 2 NO2 ——> NO3 + NO (slow) NO3 + CO ——> NO2 + CO2 (fast) What is the rate law for this reaction? A. rate = k[NO2][CO] B. rate = k[NO2]^2[CO] C. rate = k[NO2][NO3] D. rate = k[NO2]^2

D. rate = k[NO2]^2 - To answer this question, recall that the slow step of a reaction is the rate-determining step. The rate is always related to the concentrations of the reactants in the rate-determining step (not the overall reaction), so NO2 is the only compound that should be included in the correct answer. The concentration of NO2 is squared in the rate law because the question stem tells us that the system obeys second-order kinetics.