Exam 1 (CHEM 004)

When NaCl dissolves in water, aqueous Na + and Cl - ions result. The force of attraction that exists between Na + and H2O is called a(n) ________ interaction.

ion-dipole

The predominant intermolecular force in CaBr 2 is ________.

ionic bonding

As a gaseous element condenses, the atoms become ________ and they have ________ attraction for one another.

less separated, more

What is the physical phase of the substance at T = 225 K and P = 1.1 atm?

liquid

Which concentration becomes smaller as the temperature is increased from 25°C to 60°C?

molarity

In the ________ liquid crystalline phase, the component molecules exhibit only one dimensional ordering.

nematic

Which transition could occur if a solid is heated at a pressure below the triple point pressure?

sublimation

The normal boiling point occurs when the

vapor pressure of a pure liquid equals an external pressure of one atmosphere.

) Which of the following forms a molecular solid?

water

The vapor pressure of any substance at its normal boiling point is

1 atm

To make a 0.125 m solution, one could take 0.125 moles of solute and add

1.00 kg of solvent.

What is the molality of a glucose solution prepared by dissolving 27.0 g of glucose, C6H12O6, in 125.9 g of water?

1.19 m

What fraction of collisions will have sufficient energy to react for a gas whose activation energy is 68 kJ/mol at 25°C?

1.2 × 10^-12

The reaction that occurs in a Breathalyzer, a device used to determine the alcohol level in a person's bloodstream, is given below. If the rate of appearance of Cr2(SO4)3 is 1.24 mol/min at a particular moment, what is the rate of disappearance of C2H6O at that mom ent? 2 K2Cr2O7 + 8 H2SO4 + 3 C2H6O 2 Cr2(SO4)3 + 2 K2SO4 + 11 H2O

1.86 mol/min

For the first-order reaction, 2 N2O(g) 2 N2(g) + O2(g), what is the concentration of N2O after 3 half-lives if 0.15 mol of N2O is initially placed into in a 1.00-L reaction vessel?

1.9 × 10-2 M

The enthalpy change for converting 1.00 mol of ice at -25.0 °C to water at 50.0 °C is ___ kJ. The specific heats of ice, water, and steam are 2.09 J/g-K, 4.18 J/g-K, and 1.84 J/g-K respectively. For H2O, ΔH fus = 6.01 kJ/mol, and ΔH vap = 40.68 kJ/mol.

10.71

How much heat (kJ) is required to convert 3.12 moles of liquid benzene at 75.1°C to gaseous benzene at 115.1°C? The following information may be useful. b.p = 80.1°C Cm (liquid benzene) = 136.0 J/ (mol * °C) Hvap = 30.72 kJ/mol Cm (gaseous benzene) = 36.6 J/ (mol * °C)

102.0

How many grams of KBr are required to make 850. mL of a 0.115 M KBr solution?

11.6 g

What volume of a 0.716 M KBr solution is needed to provide 10.5 g of KBr?

123 mL

A solution is prepared by dissolving 17.75 g sulfuric acid, H2SO4, in enough water to make exactly 100.0 mL of solution. If the density of the solution is 1.1094 g/mL, what is the weight % H2SO4 in

16.00%

The relative initial rates of the reaction A2 + B2 ---> products in vessels (a)-(d) are 1:1:4:4. Unshaded spheres represent A2 molecules, and shaded spheres represent B2 molecules present at the beginning of the reaction. What is the order of reaction with respect to B2?

2

While mercury is very useful in barometers, mercury vapor is toxic. Given that mercury has a ̇Hvap of 59.11 kJ/mol and its normal boiling point is 356.7°C, calculate the vapor pressure in mm

2.79 x 10^-3 mm Hg

What is the molality of ethanol in a solution made by dissolving 7.30 g of ethanol, C2H5OH, in 53.6 g of water?

2.96 m

How many grams of KBr are required to make 250. mL of a 0.115 M KBr solution?

3.42 g

The vapor pressure of liquid chloroform, CHCl3, is 400.0 torr at 24.1°C and 100.0 torr at -6.3°C. What is ̇Hvap of chloroform?

30.1 kJ/mol

The normal boiling point of this substance is approximately

300°C.

Bromine is one of only two elements that is a liquid at room temperature. Bromine has a heat of vaporization of 30.91 kJ/mol and its boiling point is 59°C. What is the entropy of vaporization for bromine?

93.1 J/(mol · K)

Which of the following does not affect the rate of a bimolecular reaction?

All of these affect the rate

Which of the following liquids will exhibit the highest vapor pressure?

Br2, bp = 58.8°C

The solid and liquid phases can exist in equilibrium along line

CB

Melting occurs along the

CB line

Of the following, ________ should have the highest critical temperature.

CBr4

Which of the following substances has the highest boiling point?

CH3-CH2-CH2-CH2-CH3

Arrange the following compounds in order of their expected increasing solubility in water: NaF, CH3CH2-O-CH2CH3, CH3CH2CH2CH2-OH, CH3CH2CH2CH3 .

CH3CH2CH2CH3 < CH3CH2-O-CH2CH3 < CH3CH2CH2CH2-OH < NaF

Which one of the following derivatives of methane has the highest boiling point?

CI4

The following diagram shows a close-up view of the vapor pressure curves for a pure solvent and a solution containing a nonvolatile solute dissolved in this solvent. Which curve is the solvent and what happens to the vapor pressure when the solute is dissolved in the solvent?

Curve (a) is the solvent and the vapor pressure decreases

The layers of graphite are held together by

London dispersion forces

Which transition could occur if a solid is heated at a pressure above the triple point pressure?

Melting (Solid ---> Liquid)

Which cation in each set is expected to have the larger (more negative) hydration energy? I. Mg2+ or Ca2+ II. Li+ or Al3+

Mg2+ in set I and Al3+ in set II

Which of the following molecules has hydrogen bonding as its only intermolecular force?

None, all of the above exhibit dispersion forces.

The following set of data was obtained by the method of initial rates for the reaction: BrO3 -(aq) + 5 Br-(aq) + 6 H+(aq) ---> 3 Br2(aq) + 3 H2O(l). What is the rate law for the reaction?

Rate = k[BrO3 -][Br-][H+]2

The reaction below is first order in H2 and second order in NO. What is the rate law for this reaction? 2 H2(g) + 2 NO(g) ---> N2(g) + 2 H2O(g)

Rate = k[H2][NO]2

For the zeroth-order reaction: A ---> products, what will happen to the rate of reaction if the concentration of A is tripled?

The rate will remain the same.

9) In which case should CO2(g) be more soluble in water?

The total pressure is 4 atm and the partial pressure of CO2 is 3 atm.

An aqueous reaction occurs by a two-step mechanism, shown below. Step 1: A2X2 + Y ---> A2X + XY Step 2: A2X2 + XY ---> A2X + X2 + Y What is the catalyst in this reaction?

Y

Which of the following statements is not consistent with the properties of a molecular solid?

a compound that conducts electricity when molten

For the reaction shown below, what is the order of reaction with respect to Br ? ClO2 -(aq) + 4 Br-(aq) + 4 H+(aq) ---> Cl-(aq) + 2 Br2(aq) +2 H2O(l)

can't tell from the information provided

A phase diagram of temperature versus composition for a mixture of the two volatile liquids octane (bp = 69°C) and decane (bp = 126°C) is shown. Assume that the vapor at point c is condensed and reboiled. What is the liquid composition of the condensed vapor prior to reboiling?

composition at point d

Based on the relative strengths of the intermolecular forces of attraction of each substance, which is the most likely vapor pressure vs. temperature curve for diethyl ether?

curve (a)

As a liquid evaporates at a temperature below its boiling point, the temperature of the liquid

decreases

Which of the following compounds forms a covalent network solid?

diamond

Which of the following is an allotrope of carbon?

diamond

Two beakers, one with pure water (light gray) and the other with an aqueous solution of KBr (dark gray), are placed in a closed container represented by drawing (a). Which of the drawings (a)-(d) represents what the beakers will look like after a substantial amount of time has passed?

drawing (b)

To make a 0.125 M solution, one could take 0.125 moles of solute and add

enough solvent to make 1.00 L of solution.

If figure (1) represents the vapor pressure of water at 25°C in a 1 liter container, which figure represents the vapor pressure of water at 25°C in a 2 liter container?

figure (3)

If figure (1) represents the vapor pressure of water at 25°C, which figure represents the vapor pressure of ethanol, CH3CH2OH at 25°C?

figure (3)

If figure (1) represents the vapor pressure of water at 25°C, which figure represents the vapor pressure of water at 45°C?

figure (3)

Which of the following solutions will have the lowest freezing point?

0.015 m SrBr2

A solution is prepared by dissolving 17.75 g sulfuric acid, H2SO4, in enough water to make 100.0 mL of solution. If the density of the solution is 1.1094 g/mL, what is the mole fraction H2SO4 in the solution?

0.0338

A 2.00 M solution of CaCl2 in water has a density of 1.17 g/mL. What is the mole fraction of CaCl2?

0.0366

Which of the following pairs of solutions have roughly the same boiling point elevation?

0.100 m C6H12O6 and 0.0333 m CuF2

Nitrogen dioxide decomposes at 300°C via a second-order process to produce nitrogen monoxide and oxygen according to the following chemical equation. 2 NO2(g) ---> 2 NO(g) + O2(g). A sample of NO2(g) is initially placed in a 2.50-L reaction vessel at 300°C. If the half-life and the rate constant at 300°C are 44 seconds and 0.54 M-1 s-1, respectively, how many moles of NO2 were in the original sample?

0.11 mol

What is the mole fraction of ethanol in a solution made by dissolving 25.0 g of ethanol, C2H5OH, in 53.6 g of water?

0.154

What is the approximate vapor composition above a boiling solution that is 0.70 XA and 0.30 XB?

0.30 XA, 0.70 XB

What is the mole fraction of oxygen in a gas mixture that is 40.0% oxygen and 60.0% nitrogen by volume?

0.368

The temperature and pressure at which all three phases can coexist in equilibrium is

0.45 atm and 130°C

At 80°C, pure liquid A has a vapor pressure of 700 mm Hg and pure liquid B has a vapor pressure of 940 mm Hg. What is XA for a solution of A and B with a normal boiling point of 80°C?

0.75

) At a given temperature the vapor pressures of benzene and toluene are 183 mm Hg and 59.2 mm Hg, respectively. Calculate the mole fraction of benzene in the vapor phase over a solution of benzene and toluene with Xbenzene = 0.600

0.823

Sodium hydroxide is available commercially as a 50.0% by weight aqueous solution. The density of the solution is 1.53 g/mL. Calculate the molarity of this sodium hydroxide solution.

19.1 M

The aquation of tris(1, 10-phenanthroline)iron(II) in acid solution takes place according to the equation: Fe(phen)3 2+ + 3 H3O+ + 3 H2O ---> Fe(H2O)6 2+ + 3 phenH+ If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10-3 min-1, what is the rate constant at 50°C?

2.2 × 10-1 min-1

What is the weight percent of vitamin C in a solution made by dissolving 1.30 g of vitamin C, C6H8O6, in 55.0 g of water?

2.31 %

CFC-11 (trichlorofluoromethane, CCl3F) has been used for many years as the working fluid in refrigerators. Given its heat of vaporization is 26.88 kJ/mol and its entropy of vaporization is 90.51 J/(mol · K), what is the boiling point of CFC-11?

23.8°C

Ethyl chloride, C2H5Cl, is used as a local anesthetic. It works by cooling tissue as it vaporizes. The heat of vaporization is 26.4 kJ/mol. How much heat could be removed by 60.0 g of ethyl chloride?

24.6 kJ

At 25.0°C, a solution has a concentration of 3.179 M and a density of 1.260 g/mL. The density of the solution at 50.0°C is 1.249 g/mL. What is the molarity of the solution at 50.0°C?

3.151 M

The phase diagram of a substance is shown below. The approximate boiling point of this substance is

300 K

A solution of a nonelectrolyte solution contains 30.0 g of solute dissolved in 250.0g of water. The freezing point of the water is observed to be -2.50ɃC. The Kf for water is 1.86 ɃC/m and normal freezing point of water is 0.00ɃC. What is the molar mass of the substance?

335 g/mol

The following reaction is first order: C2H6 ---> 2 CH3. If the rate constant is equal to 5.5 × 10-4 s-1 at 1000 K, how long will it take for 0.35 mol of C2H6 in a 1.00 L container to decrease to 0.10 mol in the same container?

38 min

How much heat is released when 125.0 g of steam at 100.0°C is cooled to ice at -15.0°C? The enthalpy of vaporization of water is 40.67 kJ/mol, the enthalpy of fusion for water is 6.01 kJ/mol, the molar heat capacity of liquid water is 75.4 J/(mol · °C), and the molar heat capacity of ice is 36.4 J/(mol · °C).

380 kJ

The reaction: 2 HI ---> H2 + I2, is second order and the rate constant at 800 K is 9.70 × 10-2 M-1 s-1. How long will it take for 8.00 × 10-2 mol/L of HI to decrease to one-fourth of its initial concentration?

387 s

A kitchen pressure cooker operates at 1.70 atm. The ̇Hvap of water is 40.7 kJ/mol. What is the boiling point of water in the pressure cooker?

389 K

The aquation of tris(1,10-phenanthroline)iron(II) in acid solution takes place according to the equation: Fe(phen)3 2+ + 3 H3O+ + 3 H2O ---> Fe(H2O)6 2+ + 3 phenH+ If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10-3 min-1, what is the rate constant at 40°C?

4.8 × 10^-2 min-1

For a particular first-order reaction, it takes 48 minutes for the concentration of the reactant to decrease to 25% of its initial value. What is the value for rate constant (in s-1) for the reaction?

4.8 × 10^-4 s^-1

The decomposition of dinitrogen pentoxide is described by the chemical equation 2 N2O5(g) ---> 4 NO2(g) + O2(g) If the rate of appearance of O2 is equal to 2.40 mol/min at a particular moment, what is the rate of disappearance of N2O5 at that moment?

4.80 mol/min

Lead has a radius of 154 pm and crystallizes in a face-centered cubic unit cell. What is the edge length of the unit cell?

436 pm

Formaldehyde is a carcinogenic volatile organic compound with a permissible exposure level of 0.75 ppm. At this level, how many grams of formaldehyde are permissible in a 6.0-L breath of air having a density of 1.2 kg/m3?

5.4 × 10-6 g formaldehyde

The aquation of tris(1, 10-phenanthroline)iron(II) in acid solution takes place according to the equation: Fe(phen)3 2+ + 3 H3O+ + 3 H2O ---> Fe(H2O)6 2+ + 3 phenH+ If the activation energy is 126 kJ/mol and frequency factor is 8.62 × 1017 s-1, at what temperature is the rate constant equal to 3.63 × 10-3 s-1 for the first-order reaction?

50°C

What is the approximate boiling temperature of the liquid formed from the condensation of the vapor above a boiling solution that is 0.70 XA and 0.30 XB?

55°C

Calculate the enthalpy change (in kJ) associated with the conversion of 25.0 grams of ice at -4.00 °C to water vapor at 109.0 °C. The specific heats of ice, water, and steam are 2.09 J/g-K, 4.18 J/g-K, and 1.84 J/g-K, respectively. For H2O, ΔH fus = 6.01 kJ/mol and ΔH vap = 40.67 kJ/mol.

75.9

The first-order reaction, SO2Cl2 SO2 + Cl2, has a rate constant equal to 2.20 × 10-5 s-1 at 593 K. What percentage of the initial amount SO2Cl2 will remain after 3.00 hours?

78.9%

When cubic unit cells stack together, how many unit cells share a common corner?

8

Aqueous solutions of 30% (by weight) hydrogen peroxide, H2O2, are used to oxidize metals or organic molecules in chemical reactions. Given that the density of the solution is 1.11 g/mL, calculate the molarity.

9.79 M

The boiling point of a liquid is 64 °C and the enthalpy change for the conversion of this liquid to the gas is 32.21 kJ/mole. What is the entropy change for vaporization, ̇Svap?

96 J/mol*K

The decomposition of ozone in the stratosphere can occur by the following two-step mechanism: Step 1: Br + O3 BrO + O2 Step 2: BrO + O Br + O2 Which species is an intermediate in this mechanism?

BrO

Which is expected to have the highest surface tension at 25°?

C3H5(OH)3

Which of the following forms a molecular solid?

C9H8O4

A three-step mechanism has been suggested for the formation of COCl2: Step 1: Cl2 ---> 2 Cl Step 2: Cl + CO ---> COCl Step 3: COCl + Cl2 ---> COCl2 + Cl Which species is an intermediate in the mechanism?

COCl

Of the following substances, ________ has the highest boiling point.

H2O

Which of the following compounds has the highest boiling point?

H2O

Has hydrogen bonding as one its IMF

H5-C-N

Which of the following compounds has the highest boiling point?

HOCH2CH2OH

Two aqueous solutions, A and B, are separated by a semipermeable membrane. The osmotic pressure of solution A immediately begins to decrease. Which of the following statements is true?

Solvent molecules are moving from solution B into solution A.

______ is the energy required to expand the surface area of a liquid by a unit amount of area.

Surface Tension

Which of the following should most favor the solubility of an ionic solid in water?

a low lattice energy for the solid and a high hydration energy for its ions

Which arrow represents ̇Hsolute-solvent?

arrow (c)

Which arrow represents ̇Hsoln?

arrow (d)

For a given substance that exhibits liquid-crystalline properties, the transition from solid to liquid-crystal state occurs ________.

at the melting point of the solid

The decomposition of cyclopropane, was observed at 500°C and its concentration was monitored as a function of time. The data set is given below. What is the order of the reaction with respect to cyclopropane?

first

The half life of the reaction shown below is found not to depend on the concentration of H2O2(aq). 2 H2O2(aq) ---> 2 H2O(l) + O2(g) What is the order of this reaction?

first

Which is not a solution?

fog

What is the physical phase of the substance at T = 400 K and P = 2.0 atm?

gas

Which of the following forms a metallic solid?

gold

Over the time interval 300 to 400 seconds, the rate of reaction with respect to A is ̇[A]/̇t = 3.7 × 10-5 M/s. What is the rate of reaction with respect to A over the time interval 0 to 100 seconds?

greater than 3.7 × 10-5 M/s

What is the predominant intermolecular force in H 2NNH 2?

hydrogen bonding

Which of the intermolecular forces is the most important contributor to the high surface tension shown by water?

hydrogen bonding

For which case would ̇Hsoln be expected to be negative?

if solute-solvent interactions are much greater than solvent-solvent and solute-solute interactions

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 A is increased by a factor of 1.50? The rate will

increase by a factor of 1.50

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 A is increased by a factor of 3.00? The rate will

increase by a factor of 3.00

One reason ionic compounds do not dissolve well in nonpolar solvents is that

ion-solvent interactions are not strong enough to solvate the ions in solution.

Which of the following characteristics would prevent liquid crystal behavior?

ionic configuration

According to the diagram, the solid phase of this substance

is more dense than the liquid phase.

Over the time interval 300 to 400 seconds, the rate of reaction with respect to A is ̇[A]/̇t = 3.7 × 10-5 M/s. What is the rate of reaction with respect to A over the time interval 700 to 800 seconds?

less than 3.7 × 10-5 M/s

For a liquid solution made by dissolving a solid or a gas in a liquid, the

liquid is the solvent

The first-order decomposition of hydrogen peroxide occurs according to the equation 2 H2O2(aq) 2 H2O(l) + O2(g)

ln[H2O2] versus time

Which type of bonding does sucrose form upon solidification?

molecular

The solubility of gaseous solutes in liquid solvents is greater when the

partial pressure of the gas above the solution is increased.

The following reaction is first order in A and first order in B: A + B Products Rate = k[A][B] What is the rate constant k of this reaction in vessel (b) relative to the rate constant k of this reaction in vessel (a)? Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded spheres represent B molecules.

rate constant k in vessel (b)/rate constant k in vessel (a) = 1:1

The following reaction is first order in A and first order in B: A + B Products Rate = k[A][B] What is the initial rate of this reaction in vessel (b) relative to the initial rate of this reaction in vessel (a)? Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded spheres represent B molecules present at the beginning of the reaction

rate in vessel (b)/rate in vessel (a) = 2:1

Consider a reaction that occurs by the following mechanism: A + BC ---> AC + B AC + D ---> A + CD Intermediates occur at which reaction stages?

reaction stages 2 and 4

What phase changes occur when the pressure is held constant at 0.25 atm and the temperature increases from 100°C to 300°C?

solid ---> gas

In most liquid solutions, the component present in the larger amount is called the

solvent

The magnitude of the heats of vaporization, fusion and sublimation of a substance reflect the

strength of the intermolecular forces of the substance.

The property of a liquid that measure the liquid's resistance to spread out and increase its surface area is

surface tension

Which of the following mixtures have components which can be separated by filtration?

suspensions

A phase diagram of temperature versus composition for a mixture of the two volatile liquids octane (bp = 69°C) and decane (bp = 126°C) is shown. Assume that the vapor at point c is condensed and reboiled. What is the boiling point?

temperature at point d

The vapor pressure of a pure liquid increases as the

temperature of the liquid phase increases.

When a liquid is heated at its boiling point, the

temperature of the liquid remains the same as long as any liquid is present.

For a particular compound, which is expected to be the largest in general?

the molar heat of vaporization at the normal boiling point

Commercial cold packs often contain solid NH4NO3 and a pouch of water. The temperature of the pack drops as the NH4NO3 dissolves in water. Therefore, for the dissolving of NH4NO3 in water,

̇Hsoln is positive and ̇Ssoln is positive.

Although there are exceptions, which is most likely to be true for the dissolving of a solid in a liquid?

̇Ssoln is positive.