chem sem 1 final nooooo

According to the information above, what is the standard enthalpy of formation, ΔH°f, for NH3(g) at 298 K?

a; -46 kJ/mol

If 50. mL of 1.0 M NaOH is diluted with distilled water to a volume of 2.0 L, the concentration of the resulting solution is

a; 0.025 M

On the basis of the information above, which of the following arranges the binary compounds in order of increasing bond polarity?

a; CH4 < SiCl4 < SF4

Which of the following techniques would be best to investigate molecular vibrations in molecules of the red dye?

a; Infrared spectroscopy

Which of the following is a list of the minimum amount of data needed for determining the molar enthalpy of solution of KCl(s) in pure H2O(l) ? (Assume that the KCl(aq) has the same specific heat capacity as pure water and that the initial temperatures of the KCl(s) and the water are the same.)

a; Mass of KCl(s), mass of H2O, initial temperature of the water, and final temperature of the solution

When nitrogen and oxygen gas combine in a synthesis reaction, the reaction vessel decreases in temperature. The reaction has an energy profile similar to the graph represented above. Is this an endothermic or exothermic reaction and why?

a; This is an endothermic reaction. A decrease in temperature reflects energy being absorbed from the surroundings, the products end with more potential energy than the reactants.

At standard temperature and pressure, a 0.50 mol sample of H2 gas and a separate 1.0 mol sample of O2 gas have the same

a; average molecular kinetic energy

A sample of a solid substance conducts electricity in both the solid and liquid phase. Which of the following types of interactions is most likely found between particles in the substance?

b; metallic bonds

The mass spectrum of an average sample of a pure element is shown above. Which of the following is the identity of the element?

b;Nb

For which of the following molecules are resonance structures necessary to describe the bonding satisfactorily?

b;SO2

What do each of the peaks on this mass spectrum represent?

b;number of electrons

What is the flow of heat in the reaction represented above?

c; -392 kJ

The gas-phase reaction is assumed to occur in a single step. Two experiments were done at the same temperature inside rigid containers. The initial partial pressures of and used in experiment 1 were twice the initial pressures used in experiment 2. Which statement provides the best comparison of the initial rate of formation of in experiments 1 and 2 ?

c;The initial rate of formation of is faster in experiment 1 than in experiment 2 because at a higher pressure the collisions between and molecules would have been more frequent, increasing the probability of a successful collision.

In the diagram above, which of the labeled arrows identifies hydrogen bonding in water?

d;

Which of the following modifications will increase the rate of the reaction the most?

d; Using eggshells that are more finely powdered than those used in the original experiment

A student has a sample of each of the following compounds: , , and . Which of the following lists the samples in order of increasing number of moles in the sample?

d; kbr<kcl<nacl

In the visible spectrum of light, which color listed below has the longest wavelength?

d; red

A student wanted to determine the molarity of lead(II) nitrate in a solution. She added a large excess of sodium carbonate solution to a sample of the Pb(NO3)2 solution. The lead(II)carbonate precipitate was collected via filtration and dried. After analyzing the data, the student results suggested the lead(II) nitrate concentration was 3% higher than expected. Which of the following could account for this error?

d; the precipitate was not rinsed with distilled water after collection

Based on the reaction represented by the chemical equation shown above, what is the amount of heat released when 8.00mol of H2S(g) reacts with 9.00mol of O2(g)?

d; −3360kJ

Silicon crystals are semiconductors. Which of the following is a correct reason for the increase in the conductivity of Si crystals when a small fraction of Si atoms are replaced with those of a different element?

a; P atoms introduce additional mobile negative charges.

An unknown metal, M, was heated and the heating curve above was created. At what point(s) would a mixture of a solid and liquid be present?

a; Points B and C.

Which of the following is a rate law, where the units of rate are equal to the units of the rate constant?

a; Rate = k [A]0

A possible mechanism for the overall reaction represented above is the following. 1. NO(g) + NO(g) → N2O2(g) slow ;2. N2O2(g) + O2(g) → 2NO2(g) fast ;Which of the following rate expressions agrees best with this possible mechanism?

a; Rate = k[NO]2

The potential energy of a system of two atoms as a function of their internuclear distance is shown in the diagram above. Which of the following is true regarding the forces between the atoms when their internuclear distance is x?

a; The attractive and repulsive forces are balanced, so the atoms will maintain an average internuclear distance x.

In his atomic theory, Dalton proposed that all atoms of a given element are identical. Which of the following observations provides the best evidence that the proposal is incorrect?

a; The mass spectrum of has a peak at and another peak at 65 amu.

2 MnO41- + 16 H+ + 5 C2O42-®10 CO2(g) + 2 Mn2+(aq) + 8 H2O(l) Which element is being oxidized, and what is the change in oxidation number?

a; carbon from +3 to +4

Which of the following expressions is equivalent to ΔHofor the reaction represented above?

a; x + 2y

The photoelectron spectra for and are represented above. Which of the following statements best accounts for the fact that the peak on the spectrum is farther to the left and higher than the peak on the spectrum?

b has a greater nuclear charge than and an additional electron in the same energy level.

The oxidation of carbon monoxide can be represented by the chemical equation . The table above provides the average bond enthalpies for different bond types. Based on the information in the table, which of the following mathematical expressions is correct for the estimated enthalpy change for the reaction?

b;

What is the formal charge of oxygen in the compound above?

b; +1

2NO(g) + \(O_2\)(g) → \(2NO_2\)(g) ΔH = −113.1kJ What is ΔH the for the decomposition of nitrogen dioxide?

b; +113.1 kJ

According to the information above, what is the standard enthalpy of formation, ΔH°f, for NH3(g) at 298 K ?

b; -46 kJ/mol

The half-reactions for the oxidation-reduction reaction between and are represented above. Based on the half-reactions, what is the coefficient for if the equation for the oxidation-reduction reaction is balanced with the smallest whole-number coefficients?

b; 2

Based on periodic trends and the data in the table above, which of the following are the most probable values of the atomic radius and the first ionization energy for potassium, respectively?

b; 242 pm, 419 kJ/mol

Which of the following best describes the flow of heat when 1.0 mol of XY2 decomposes?

b; 50 kJ of heat is transferred from the surroundings.

I2 + H2 → 2 HI ; In the reaction represented above, what mass of HI is produced by the reaction of 2.0 x 1023 molecules H2 with excess I2?

b; 85 g

Which of the following will most likely increase the rate of the reaction represented above

b; Adding a heterogeneous catalyst to the reaction system

What is/are the product(s) of the balanced net ionic equation when aqueous solutions of silver nitrate and potassium chloride are mixed?

b; AgCl(s)

Addition of sulfurous acid (a weak acid) to barium hydroxide (a strong base) results in the formation of a precipitate. The net ionic equation for this reaction is

b; H2SO3(aq) + Ba2+(aq) + 2 OH- (aq) ⇄ BaSO3(s) + 2 H2O(l)

According to the information in the table above, a 1.00 g sample of which of the following contains the greatest mass of oxygen?

b; MgO

Resonance is most commonly used to describe the bonding in molecules of which of the following?

b; O3

Which of the following can be inferred from the diagram above that shows the dependence of potential energy on the internuclear distance between 2 atoms?

b; The atoms form a bond with a bond length of 75pm.

A 1.0 mol sample of He(g) at 50°C is mixed with a 1.0 mol sample of Xe(g) at 25°C. Which of the following correctly predicts the changes in average kinetic energy and the average speed of the Xe(g) atoms that will occur as the mixture approaches thermal equilibrium?

b; The average kinetic energy of xenon atoms will increase and the average speed of the xenon atoms will increase.

A chemical reaction occurred in an insulated isolated system resulting in a decrease in the potential energy of the system. Select the true sentence.

b; The temperature of the system increased.

A sample of is heated to and placed in a calorimeter containing of water at . As the system approaches thermal equilibrium, energy is transferred

b; from the to the water and the temperature of the decreases

Based on the information for two different reactions given above, which of the following gives the quantities needed to calculate the enthalpy change for the reaction represented by the overall equation below?

c;

The heat of fusion for water is 6.01 kJ/mole and the heat of vaporization for water is 40.7 kJ/mol, how much energy is needed to melt 36 grams of ice?

c; 12kJ

2 MnO41- + 16 H+ + 5 C2O42- → 10 CO2(g) + 2 Mn2+(aq) + 8 H2O(l) In a titration experiment, C2O42- reacts MnO4- with as represented by the equation above. The dark purple KMnO4 solution is added from a buret to an acidified colorless solution in an Erlenmeyer flask. At some point in the experiment, the rate of appearance of Mn2+ ions was 1.0 x 10-4M/s. What was the rate of disappearance of C2O42-?

c; 2.5 x 10^-4M/s

What is the ΔHof, for C2H2(g)? Where: ΔHof of C6H6(g) is 83 kJ mol-1

c; 230 kJ mol-1

. When 5.0 g of NH4ClO4(s) is added to 100. mL of water in a calorimeter, the temperature of the solution formed decreases by 3.0°C. If 5.0 g of NH4ClO4(s) is added to 1000. mL of water in a calorimeter initially at 25.0°C, the final temperature of the solution will be approximately

c; 24.7°C

The half-reactions for the oxidation-reduction between Al(s) and (aq) are represented above. Based on the half-reactions above what is the coefficient for Zn(s) if the equation for the oxidation -reduction reaction is balanced with the smallest whole-number coefficients?

c; 3

Has a central atom with less than an octet of electrons

c; BH3

Of the following organic compounds, which is LEAST soluble in water at 298 K?

c; C6H14, hexane

The complete photoelectron spectra of neutral atoms of two unknown elements, X and Y, are shown above. Which of the following can be inferred from the data?

c; Element Y has a greater nuclear charge than element X does.

The complete photoelectron spectrum for an element is shown above. Which of the following observations would provide evidence that the spectrum is consistent with the atomic model of the element?

c; In its compounds, the element tends to form ions with a charge of +1.

On the basis of molecular structure and bond polarity, which of the following compounds is most likely to have the greatest solubility in water?

c; NH3

Which combination of statements is consistent with the data above

c; Rate = k [A]2 [B] and the overall reaction is 3A + B → 2C + D

Based on the data above, what can be concluded regarding the strength of the C-H, N-H, and O-H bonds in the molecules shown?

c; The O-H bond is the strongest.

A 1.0 g sample of a cashew was burned in a calorimeter containing 1000. g of water, and the temperature of the water changed from 20.0°C to 25.0°C. In another experiment, a 3.0 g sample of a marshmallow was burned in a calorimeter containing 2000. g of water, and the temperature of the water changed from 25.0°C to 30.0°C. Based on the data, which of the following can be concluded about the energy content for 1.0 g of each of the two substances? (The specific heat of water is 4.2 J/(g⋅°C).)

c; The combustion of 1.0 g of cashew releases more energy than the combustion of 1.0 g of marshmallow.

Cl−(aq) + ClO−(aq) + 2 H+(aq) → Cl2(g) + H2O(l) What effect will increasing [H+] at constant temperature have on the reaction represented above?

c; The frequency of collisions between H+ (aq) ions and ClO−(aq) ions will increase.

A student was asked to formulate a hypothesis about what would happen if of at was combined with of at . Which of the following hypotheses indicates that the student thought a chemical change would occur?

c; The resulting solution would contain a precipitate.

Solid carbon tetrachloride, , is represented by the diagram above. The attractions between the molecules that hold the molecules together in the solid state are best identified as

c; intermolecular attractions resulting from temporary dipoles

What is element represented by the diagram above?

c; molybdenum (element #42)

A rigid 10.0 L container holds neon gas at a very high pressure. The measured pressure is much larger than the pressure predicted by the ideal gas law. Which of the following is the best explanation for this? (A) neon atoms break into two boron atoms at high pressure

c; the volume of the neon atoms is too large a fraction of the volume of the container to be negligible

On the basis of the molecular structure and bond polarity, which of the following compounds is most likely to have the greatest solubility in water?

c;NH3

Which situation best describes a successful collision (one that leads to a chemical reaction)?

c;The reactants collide with sufficient energy and the correct orientation

NH3 reacts with BF3 to form a single species. Which of the following structural diagrams is the most likely representation of the product of the reaction?

d;

Which of the following equations best represents the reacting species in the reaction between metal and ?

d;

Which of the following graphs correctly shows the relationship between potential energy and internuclear separation for two hydrogen atoms?

d;

A sample of a solid organic compound is completely combusted in a calorimeter. The heat generated by combustion is transferred to the water, causing the temperature of the water to increase. Based on the data in the table above, which of the following is the best estimate of the heat of combustion, , of the organic solid? (The specific heat of water is )

d; -18 kJ/g

The concentration of ions in solution was

d; 0.080 M

When a student adds 30.0 mL of 1.00 M HCl to 0.56 g of powdered Fe, a reaction occurs according to the equation above. When the reaction is complete at 273 K and 1.0 atm, which of the following is true?

d; 0.22 L of H2 has been produced.

How many sets of lone pair electrons exist on a molecule of carbon tetrafluoride?

d; 12

The table above shows the results from a rate study of the reaction X + Y → Z. Starting with known concentrations of X and Y in experiment 1, the rate of formation of Z was measured. If the reaction was first order with respect to X and second order with respect to Y, the initial rate of formation of Z in experiment 2 would be

d; 2R

A sample of ice at is added to of water at . The mixture is stirred gently until the temperature of the water is . All the remaining ice is quickly removed. Based on the information in the table above, the mass of ice that melted is closest to

d; 42 g

.....C5H12(l) + ....O2(g) → ....H2O(g) + ....CO2(g) ;When the equation for the reaction represented above is balanced and all coefficients are reduced to the lowest whole-number terms, the coefficient for O2 is

d; 8

The first ionization energy of an element is the energy required to remove an electron from a gaseous atom of the element (i.e., X(g) → X+(g) + e−). The values of the first ionization energies for the third-row elements are shown in the graph above. On the basis of the information given, which of the following reactions is exothermic?

d; Al(g) + Mg+(g) → Al+(g) + Mg(g)

Which of the following correctly identifies which has the higher first-ionization energy, Cl or Ar, and supplies the best justification?

d; Ar, because of its higher effective nuclear charge

According to the information in the table above, a 10.0 gram sample of which of the following has the greatest mass of chlorine?

d; BeCl2

Which of the following liquids experiences dipole-dipole intermolecular forces?

d; CF2Cl2

According to the complete photoelectron spectrum, which of the following is the identity of the element?

d; Ne

Which of the following correctly identifies which has the higher first-ionization energy, F or Ne, and supplies the best justification?

d; Ne, because of its higher effective nuclear charge

The photoelectron spectra above show the energy required to remove a 1s electron from a nitrogen atom and from an oxygen atom. Which of the following statements best accounts for the peak in the upper spectrum being to the right of the peak in the lower spectrum?

d; Nitrogen atoms have a smaller nuclear charge than oxygen atoms.

Which of the following scientific claims about the bond in the molecular compound is most likely to be true?

d; The bond is highly polar.

15.0 grams of calcium chloride is dissolved into 100.0 mL of water at 22.5°C, the final temperature of the solution was 32.2°C. Select the correct response.

d; The dissolution process was exothermic and the kinetic energy of the water increased.

Consider the following mechanism for the reaction represented above. ;Step 1: 2 NO ⇄ N2O2 (fast reversible) ;Step 2: N2O2 + O2 → 2 NO2 (slow);Which of the following statements is true?

d; The rate law that is consistent with the mechanism is rate = k[NO]2[O2].

The formation of magnesium oxide, MgO, is shown below: Mg(s) + ½ (g) → MgO(s) - 601.7 kJ Is this an endothermic or exothermic reaction and why?

d; The reaction is exothermic because the enthalpy is written on the product side.

Which of the following statements correctly identifies which compound, pentane or propanoic acid, has the higher boiling point and provides a valid justification?

d;Propanoic acid, because it forms hydrogen bonds, whereas pentane does not

When water is left in a container at room temperature over a period of time, the water "disappears" from the container. Is this an endothermic or exothermic process? Select the correct reasoning for your choice.

d;The process is endothermic since energy is being absorbed to change liquid water to gaseous water.

Based on the information above, what is the enthalpy change for the sublimation of iodine, represented below?

e; 62 kJ/molrxn