Chem 2 Unit 1 Test Ch 10-15

Assign the appropriate labels to the phase diagram shown below. A = liquid, B = solid, C = gas, D = critical point A = solid, B = gas, C = liquid, D = critical point A = gas, B = solid, C = liquid, D = triple point A = liquid, B = gas, C = solid, D = critical point A = gas, B = liquid, C = solid, D = triple point

A = gas, B = solid, C = liquid, D = triple point

Which of the following has the greatest electronegativity difference between the bonded atoms? A strong acid made of hydrogen and a halogen, such as HCl A diatomic gas, such as nitrogen (N2). A group 1 alkali metal bonded to bromide, such as KBr. Carbon bonded to a group 6A (16) nonmetal chalcogen, such as in CO

A group 1 alkali metal bonded to bromide, such as KBr. The electronegativity difference between K and Br is 2.0, according to the table provided. This is higher than the other calculated values.

Shape and expansion

A solid does not take the shape of its container, nor does it expand to fill the container. A liquid takes the shape of its container but does not expand to fill it. A gas takes the shape of its container and expands to fill it.

Identify an ionic bond. Protons are pooled. Neutrons are shared. Neutrons are gained. Electrons are transferred. Neutrons are lost.

Electrons are transferred.

Nonpolar covalent

H-H

dipole-dipole

exists between all molecules that are polar. Polar molecules have electron-rich regions (which have a partial negative charge) and electron-deficient regions (which have a partial positive charge). For example, consider acetone The image on the right is an electrostatic potential map of acetone; we first saw these kinds of maps in Sections 10.6 and 11.5. Recall that the red areas indicate electron-rich regions in the molecule and that the blue areas indicate electron-poor regions. Notice that acetone has an electron-rich region surrounding the oxygen atom (because oxygen is more electronegative than the rest of the molecule) and electron-poorer regions surrounding the carbon and hydrogen atoms. The result is that acetone has a permanent dipole that can interact with other acetone molecules as shown in Figure 12.7. The positive end of one permanent dipole attracts the negative end of another; this attraction is the dipole-dipole force. Polar molecules, therefore, have higher melting and boiling points than nonpolar molecules of similar molar mass. Remember that all molecules (including polar ones) have dispersion forces. Polar molecules have, in addition, dipole-dipole forces. This additional attractive force raises their melting and boiling points relative to nonpolar molecules of similar molar mass.

anions

have a negative charge

Cations

have a positive charge

What is the strongest type of intermolecular force present in Cl 2? hydrogen bonding ion-dipole dispersion dipole-dipole none of the above

dispersion

Calculate the freezing point of a solution containing 40 grams of KCl and 4400.0 grams of water. The molal-freezing-point-depression constant (Kf) for water is 1.86 ∘C/m +0.45 oC -0.45 oC +0.23 oC 1.23 oC -0.23 oC

-0.45 oC

Calculate the mole fraction of Ba Cl 2 in an aqueous solution prepared by dissolving 0.400 moles of Ba Cl 2 in 850.0 g of water. 0.0540 0.00252 0.0167 0.00900 0.00841

0.00841

Choose the aqueous solution below with the lowest freezing point. These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable. 0.075 m NaI O40.075 m KNO 20.075 m LiCN 0.075 m (NH4)3PO 40.075 m K Br

0.075 m (NH4)3PO (because largest, or highest number of ions)

A solution contains 22.4 g glucose (C6H12O6) dissolved in 0.500 L of water. What is the molality of the solution? (Assume a density of 1.00 g/mL for water.) 0.0622 m 0.338 m 0.216 m 0.249 m

0.249 m

Give the approximate bond angle for a molecule with a trigonal planar shape. 45∘ 120∘ 109.5∘ 180∘ 107∘

120∘

The following reaction proceeds at a rate such that 7 mole of A is consumed per minute. Given this, how many moles of C are produced per minute? 2A+2B→4C

14 mol

The heat of vaporization of water at 100 ∘C is 40.66 kJ/mol. Calculate the quantity of heat that is absorbed/released when 8.00 g of steam condenses to liquid water at 100∘C. 18.1 kJ of heat are absorbed. 91.6 kJ of heat are released. 18.1 kJ of heat are released. 91.6 kJ of heat are absorbed.

18.1 kJ of heat are released.

Calculate the pH for the following weak acid. A solution of HCOOH has 0.16M HCOOH at equilibrium. The KaKa for HCOOH is 1.8×10−4. What is the pH of this solution at equilibrium? Express the pH numerically.

2.27 As a rule of thumb, recall that the pH will change by 1 unit for every factor of 10 change in [H+]. So, if [H+] increases by 100, the pH value for the solution will decrease by 2 units.

How many particles would one formula unit of CaCl2 produce when dissolved in solution? 3 1 0 2

3 CaCl2 would dissociate to produce one Ca+ ion and two Cl− ions.

What is the overall order of the following reaction, given the rate law? 2NO(g) + H2(g) → N2(g) + 2H2O(g) Rate = k[NO]2[H2] 3rd order 1st order 6th order 4th order

3rd order (add exponents in rate equation 2+1=3

0.34 L of HNO3 is titrated to equivalence using 0.12 L of 0.1 MNaOH. What is the concentration of the HNO3? Express the concentration of HNO3 in molarity.

4×10−2M Balanced chemical reaction is: HNO3 + NaOH --> NaNO3 + H2O Moles of NaOH = (0.1 M) x (0.12 L) = 0.012 moles moles of HNO3 needed to neutralize = 0.012 moles Molarity of HNO3 = (0.012 mol) / (0.34 L) = 0.035 M Rounds to .004 --> 4.0x10^-2

Which has a higher entropy? 1 mole of KBr solid and water A solution of KBr in water

A solution of KBr in water Mixing of the solid KBr and the water solubilizes the KBr into its ions, K+ and Br−. The ions now have a greater molecular motion than they did as a solid. In addition, the solvent water molecules are now interspersed in solution with K+ and Br− ions. Mixing of more than one type of molecule creates greater molecular randomness of position and molecular motion than a pure liquid with only one type of molecule.

Notice in Table 1 how each force relates to molecular polarity. Which of the following would have a higher boiling point? CCl4 N2 CH2Br2 CH4

CH2Br2 Intermolecular forces depend on polarity. If you had trouble deciding if the molecules within these choices are or are not polar molecules, please review the primer tutorial about molecular polarity. It is noteworthy to mention that when ions are present along with polar molecules there also exists ion-dipole forces, another class of forces between molecules and ions and stronger than the forces between molecules. An example would include NaCl dissolved in water. The ions would include Na+ and Cl− ions in solution with polar water molecules.

Ionic

Cs−Br Ba−F

Polar covalent

C−O H−Br P-Br

Determine which intermolecular forces are the dominant (strongest) forces for a pure sample of each of the following molecules by placing the molecules into the correct bins. Dispersion forces Dipole-dipole forces Hydrogen bonding forces Cl2 Ne H2S CH2Cl2 CH3NH2 C2H5OH

Dispersion forces Cl2 Ne Dipole-dipole forces H2S CH2Cl2 Hydrogen bonding forces CH3NH2 C2H5OH It is noteworthy to mention that when ions are present with polar molecules, ion-dipole forces exist−−another class of forces between molecules and ions which are stronger than hydrogen bonding forces. An example would include NaCl dissolved in water. The ions would include Na+ and Cl− ions in solution with polar water molecules.

Summarizing Intermolecular Forces

Dispersion forces are present in all molecules and atoms and generally increase with increasing molar mass. These forces are always weak in small molecules but can be significant in molecules with high molar masses. Dipole-dipole forces are present in polar molecules. Hydrogen bonds, the strongest of the intermolecular forces that can occur in pure substances (second only to ion-dipole forces in general), are present in molecules containing hydrogen bonded directly to fluorine, oxygen, or nitrogen. Ion-dipole forces are present in mixtures of ionic compounds and polar compounds. These forces are very strong and are especially important in aqueous solutions of ionic compounds.

Which has the higher boiling point, H2OH2O or H2SH2S? Why? H2O has the higher boiling point because it exhibits hydrogen bonding. H2S has the higher boiling point because it exhibits stronger dipole-dipole forces between molecules. H2O has the higher boiling point because it exhibits stronger dispersion forces between molecules. H2S has the higher boiling point because it has the larger molar mass.

H2O has the higher boiling point because it exhibits hydrogen bonding. Hydrogen bonds can only form between a hydrogen atom that is bonded with a highly electronegative atom (i.e., NN, OO, and FF) and a highly electronegative atom on another molecule. Since SS is moderately electronegative, it will only participate in dipole-dipole interactions rather than hydrogen bonding. Therefore, only H2OH2O participates in hydrogen bonding, and it will have a higher boiling point because hydrogen bonding is a stronger intermolecular force than dipole-dipole interactions.

What are the conjugate acid-base pairs in the reaction of H2SO3 with H2O? H2SO3+H2O→products H2O/H3O+ H2SO3/HSO3− and H2O/H3O+ H2SO3/HSO3− and HSO3/SO32− H2SO3/HSO3−

H2SO3/HSO3− and H2O/H3O+ H2SO3(aq)+H2O(l)⇌HSO3−(aq)+H3O+(aq)

The following molecules contain polar bonds. Select all that are also polar molecules. Check all that apply.

HI NO2 PF3

Which molecule of the following pair has stronger dispersion forces? Heptane 2,4-Dimethylpentane

Heptane

Density

In both solids and liquids, the molecules are held very closely together and therefore their densities are about the same. In gases, there is space between the molecules.

Consider the following gas phase reaction. A+B→2CA+B→2C When the reaction begins, the researcher records that the rate of reaction is such that 1 mole of A is consumed per minute. After making changes to the reaction, the researcher notes that 2 moles of A are consumed per minute. What change could the researcher have made to effect this change? Utilize reaction conditions to convert both reactants to solids. Increase the temperature, allowing more frequent collisions of A and B with greater kinetic energy. Increase the concentration of C to allow for more frequent collisions of A and B of higher energy. Introduce a catalyst to decrease the consumption of A and B. Decrease the concentration of reactant B to allow C to be produced at a greater rate.

Increase the temperature, allowing more frequent collisions of A and B with greater kinetic energy.

Calculate the Ka for the following acid. Determine if it is a strong or weak acid. HClO2(aq) dissolves in aqueous solution to form H+(aq) and ClO2−(aq). At equilibrium, the concentrations of each of the species are as follows: [HClO2]=0.24M [H+]=0.051M [ClO2−]=0.051M Ka=92; This is a strong acid because the Ka is very large. Ka=1.1×10−2; This is a strong acid because the acid is completely dissociated in aqueous solution. Ka=1.1×10−2; This is a weak acid because the acid is not completely dissociated in solution. Ka=92; This is a weak acid because the acid is not completely dissociated in solution.

Ka=1.1×10−2; This is a weak acid because the acid is not completely dissociated in solution.

Use Lewis theory to determine the chemical formula for the compound formed between Mg and I. Mg 2 I Mg I 2 Mg I Mg 3 I 2 Mg 2 I 3

Mg I 2

Which molecule or compound below contains a nonpolar covalent bond? MgS NCl3 AgCl Na Br

NCl3

Place the following in order of increasing magnitude of lattice energy.MgO NaI Ba O NaI < Ba O < MgO MgO < NaI < Ba O NaI < MgO < Ba O Ba O < MgO < NaI MgO < Ba O < NaI

NaI < Ba O < MgO

hydrogen bonding

Polar molecules containing hydrogen atoms bonded directly to small electronegative atoms—most importantly fluorine, oxygen, or nitrogen—exhibit an intermolecular force called hydrogen bonding. HF, NH3NH3, and H2OH2O, for example, all exhibit hydrogen bonding. The hydrogen bond is a sort of super dipole-dipole force. The large electronegativity difference between hydrogen and any of these electronegative elements causes the hydrogen atom to have a fairly large partial positive charge (δ+) within the bond, while the F, O, or N atom has a fairly large partial negative charge (δ−) In addition, since these atoms are all quite small, the H atom on one molecule can approach the F, O, or N atom on an adjacent molecule very closely. The result is a strong attraction between the H atom on one molecule and the F, O, or N on its neighbor—an attraction called a hydrogen bond. For example, in HF, the hydrogen atom in one molecule is strongly attracted to the fluorine atom on a neighboring molecule (Figure 12.10). The electrostatic potential maps in Figure 12.10 illustrate the large differences in electron density that result in unusually large partial charges. Hydrogen bonds should not be confused with chemical bonds. Chemical bonds occur between individual atoms within a molecule, whereas hydrogen bonds—like dispersion forces and dipole-dipole forces—are intermolecular forces that occur between molecules. A typical hydrogen bond is only 2-5% as strong as a typical covalent chemical bond. Hydrogen bonds are, however, the strongest of the three intermolecular forces we have discussed so far. Substances composed of molecules that form hydrogen bonds have higher melting and boiling points than comparable substances composed of molecules that do not form hydrogen bonds. Water is another good example of a molecule with hydrogen bonding (Figure 12.12). Figure 12.13 plots the boiling points of the simple hydrogen compounds of the group 4A and group 6A elements. In general, boiling points increase with increasing molar mass, as expected, based on increasing dispersion forces. However, because of hydrogen bonding, the boiling point of water (100 °C) is much higher than expected based on its molar mass (18.0 g/mol). Without hydrogen bonding, all the water on our planet would be gaseous.

Which has a higher entropy for the reaction: 2NH3(g)→N2(g)+3H2(g) Products Reactants

Products

For the overall reaction below, which of the following is the correctly written rate law? Overall reaction:O3(g)+2NO2(g)→N2O5(g)+O2(g) Step 1:O3(g)+NO2(g)→NO3(g)+O2(g)slow Step 2:NO3(g)+NO2(g)→N2O5(g)fast Rate=k[O3][NO2]2 Rate=k[O3][NO2] Rate=k[O3][NO2]2[N2O5][O2] Rate=k[NO3][NO2]

Rate=k[O3][NO2] Mechanisms are proposed steps for an overall reaction to occur. Mechanisms must be proven experimentally. One way to determine the accuracy of a mechanism is to determine if the rate law for the mechanism correctly reflects how the rate of reaction changes according to the change in concentration of the reagents as described by the rate law. Consider the following rate law: rate=k[A]2 If the rate increases by being squared when A doubles, then this rate law correctly describes the rate in response to a change in the concentration of A.

Calculate the equilibrium constant for the following two reactions. The equilibrium concentration of each reactant and product is given in the box below the reaction. Rank the extent of each reaction at equilibrium by calculating the equilibrium constant. Note that the "extent of each reaction" refers to how much reactant is converted to product at equilibrium. Reaction 2, with Kc=1.5×104>Kc=1.5×104> Reaction 1, with Kc=2.3×10−2 Reaction 1, with Kc=43.8>Kc=43.8> Reaction 2, with Kc=6.8×10−5 Reaction 2, with Kc=43.8>Kc=43.8> Reaction 1, with Kc=6.8×10−5 Reaction 1, with Kc=5.09>Kc=5.09> Reaction 2, with Kc=5.4×10−3

Reaction 1, with Kc=43.8>Kc=43.8> Reaction 2, with Kc=6.8×10−5

Compressibility and thermal expansion

Since the molecules in solids and liquids are already very close together, applying pressure does not greatly affect the volume. In contrast, the space between gas molecules allows for a great deal of compressibility. Although temperature changes will cause slight variations in the volume of a solid or liquid, those variations are negligible compared to the thermal expansion of a gas.

In the following mechanism, which is the rate-determining step? Step 1:H2(g)+ICl(g)→HI(g)+HCl(g)(slow) Step 2:HI(g)+ICl(g)→I2(g)+HCl(g)(fast) Step 1 Step 2

Step 1 When writing a rate law for an overall reaction, the rate law is written using the rate-determining step of a reaction. For simplicity, the rate law is then put into terms of the overall chemical equation's reactants. You will learn this in your upcoming chemistry course when you study rate laws.

Which proposed mechanism below is a correct option for the overall reaction shown? Overall reaction: Br2(g)+CHBr3(g)→HBr(g)+CBr4(g) Sum the reactions in each proposed mechanism to determine which mechanism is valid for the overall reaction. Step 1:Br2(g)→2Br(g) Step 2:H2(g)+Br(g)+CBr3(g)→HBr(g)+CHBr3(g) Step 3:Br(g)+CBr3(g)→CBr4(g) Step 1:Br2(g)→2Br(g) Step 2:Br(g)+CHBr3(g)→HBr(g)+CBr3(g) Step 3:Br(g)+CBr3(g)→CBr4(g)

Step 1:Br2(g)→2Br(g) Step 2:Br(g)+CHBr3(g)→HBr(g)+CBr3(g) Step 3:Br(g)+CBr3(g)→CBr4(g)

Sometimes when we heat food in the microwave, the lid of the container pops off. Why does this occur? The air and water vapor inside the container are expanding. The lid of the container is expanding. The food inside the container is expanding.

The air and water vapor inside the container are expanding.

Bromide ion

The atom from which this ion is formed gains an electron to become an ion. This ion has a 1− charge. This ion has a total of 36 electrons.

1-Propanol is combusted to provide heat. The equation and the enthalpy change for the process are shown below. C3H7OH(l)+4.5O2(g)→3CO2(g)+4H2O(l)ΔH=−2,021kJ Below is a list of sentences that describe a chemical process. Choose all of the sentences that apply to the above reaction. The enthalpy change for 2C3H7OH(l)+9O2(g)→6CO2(g)+8H2O(l) is -4,042 kJ The enthalpy change for 2C3H7OH(l)+9O2(g)→6CO2(g)+8H2O(l) is 2,021 kJ This process is exothermic. The enthalpy change for 2C3H7OH(g)+9O2(g)→6CO2(g)+8H2O(l) is −−2,021 kJ This process is endothermic. This chemical process transfers heat from the system to the surroundings. The enthalpy change for 2C3H7OH(l)+9O2(g)→6CO2(g)+8H2O(l) is 4,042 kJ his chemical process transfers heat from the surroundings to the system.

The enthalpy change for 2C3H7OH(l)+9O2(g)→6CO2(g)+8H2O(l) is -4,042 kJ This process is exothermic. This chemical process transfers heat from the system to the surroundings.

Molecular movement and order

The molecules in solids are arranged in a regular pattern that does not allow for diffusion, although does allow for vibrations. The arrangement of molecules in a liquid, although not completely random, is not completely fixed. Molecules in a gas are randomly arranged and move very quickly. Gases diffuse quickly in comparison to liquids.

The reaction has not reached equilibrium.

The products are gaseous and escape the vessel into the atmosphere. The rate of the forward reaction is greater than the rate of the reverse reaction. The ratio of products to reactants is not stable. The concentration of products is increasing, and the concentration of reactants is decreasing.

The reaction has reached equilibrium.

The rate at which products form from reactants is equal to the rate at which reactants form from products. The ratio of products to reactants does not change. Chemical equilibrium is a dynamic state. The forward and reverse reactions proceed at the same rate. The state of chemical equilibrium will remain the same unless reactants or products escape or are introduced into the system. This will disturb the equilibrium. The concentrations of reactants and products are stable and cease to change.

Potassium ion

This ion forms ionic bonds with nonmetals. This ion has a 1+ charge. This ion has a total of 18 electrons. The atom from which this ion is formed loses an electron to become an ion. The neutral atom from which this ion is formed is a metal.

Sulfate ion

This is a polyatomic ion. This ion has covalent bonds and a net 2− charge. This anion could form a neutral compound by forming an ionic bond with one Ca2+.

Which has a higher entropy? Valve closed; no mixing Valve opened

Valve opened The amount of molecular randomness of the system increases when the valve is opened and the gases are mixed. A system with a mixture of molecules generally has an increased molecular randomness as compared to a pure substance.

Consider equal volumes (say 1 LL) of a given substance in the solid, liquid, and gas phases. Arrange them in order of decreasing mass based on the trend for the average substance. If the mass difference between samples is relatively small (10%% or less), rank the items as equivalent. Rank from greatest to least mass. To rank items as equivalent, overlap them.

While the density of a gas is always less than the density of the corresponding solid or liquid, the solids and liquids of the same substance may have similar densities. For example, 1 LL of copper in the solid phase would contain 8960 gg, while the liquid phase would contain 8020 gg and 1 LL of water (at 0 ∘C∘C) in the solid phase would contain 917 gg, while the liquid phase (at 4 ∘C∘C) would contain 1000 gg. This is a difference of less than 10%%.

Solid

a substance with a fixed volume and fixed shape

Liquid

a substance with a fixed volume and no fixed shape

Gas

a substance with no fixed volume or shape

dispersion

are the result of fluctuations in the electron distribution within molecules or atoms. Since all atoms and molecules have electrons, they all exhibit dispersion forces. The electrons in an atom or molecule may, at any one instant, be unevenly distributed. Imagine a frame-by-frame movie of a helium atom in which each "frame" captures the position of the helium atom's two electrons are the result of fluctuations in the electron distribution within molecules or atoms. Since all atoms and molecules have electrons, they all exhibit dispersion forces. The electrons in an atom or molecule may, at any one instant, be unevenly distributed. Imagine a frame-by-frame movie of a helium atom in which each "frame" captures the position of the helium atom's two electrons:

What is the name of the acid with the formula HBrO3? bromous acid hydrobromous acid bromic acid hydrobromic acid

bromic acid Note that for two common acids, phosphoric acid (coming from the phosphate ion) and sulfuric acid (coming from the sulfate ion), there is also an added -phor (for phosphoric) and -ur (for sulfuric). These are general exceptions that you may encounter to the rules above.

What is the name of the acid with the formula HBr? hydrobromic acid hydrobromous acid bromic acid bromous acid

hydrobromic acid You can now appreciate the ability to be able to know the names of common polyatomic anions. You might choose to memorize the following that appear in common acids: CO32− as carbonate (H2CO3 is carbonic acid.) SO42− as sulfate (H2SO4 is sulfuric acid.) PO43− as phosphate (H3PO4 is phosphoric acid.) NO3− as nitrate (HNO3 is nitric acid.)

For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of reaction if the concentration of B is increased by a factor of 2.00? The rate will increase by a factor of 4.00. increase by a factor of 2.00. decrease by a factor of 1/4.00. decrease by a factor of 1/2.00.

increase by a factor of 4.00. 2x2=4 (2 in front of B raised to the 2 so times)

VSEPR model

is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms.

The expression of concentration that provides the moles of solute per kilograms of solvent is

molality

A way to express concentration that provides the moles of solute per liter of solution is_____

molarity

If you place 5 moles of sodium chloride and 4 moles of sucrose into 11 moles of water, the______of sodium chloride would be 0.25.

mole fraction

ion-dipole

occurs when an ionic compound is mixed with a polar compound; it is especially important in aqueous solutions of ionic compounds. For example, when sodium chloride is mixed with water, the sodium and chloride ions interact with water molecules via ion-dipole forces, as shown in Figure 12.14. The positive sodium ions interact with the negative poles of water molecules, while the negative chloride ions interact with the positive poles. Ion-dipole forces are the strongest of the types of intermolecular forces discussed and are responsible for the ability of ionic substances to form solutions with water. We discuss aqueous solutions more thoroughly in Chapter 14.

What is the molecular geometry of SF4? tetrahedral trigonal pyrimidal square pyramidal square planar seesaw

seesaw

A solution is made up of 0.15 grams of sodium chloride in 1 liter of water. For this solution, the_____is sodium chloride.

solute

A solution is made up of 0.15 grams of sodium chloride in 1 liter of water. For this solution, the______is water.

solvent

Using the VSEPR model, the electron-domain geometry of the central atom in BF3 is ________. linear trigonal bipyramidal octahedral tetrahedral trigonal planar

trigonal planar