CHEM11: Ch.6 Test Bank

A 4.4-g sample of Colorado oil shale is burned in a bomb calorimeter, which causes the temperature of the calorimeter to increase by 5.0°C. The calorimeter contains 1.00 kg of water (heat capacity of H2O = 4.184 J/g°C) and the heat capacity of the empty calorimeter is 0.10 kJ/°C. How much heat is released per gram of oil shale when it is burned?

4.9 kJ/g

CH4(g) + 4Cl2(g) → CCl4(g) + 4HCl(g), ΔH = -434 kJ Based on the above reaction, what energy change occurs when 1.2 moles of methane (CH4) reacts?

5.2 × 105 J are released.

What is the kinetic energy of a 1.56-kg object moving at 94.0 km/hr?

5.32 × 102 kJ

Calculate the work associated with the compression of a gas from 121.0 L to 80.0 L at a constant pressure of 13.1 atm.

537 L atm

When a 21.1-g sample of ethyl alcohol (molar mass = 46.07 g/mol) is burned, how much energy is released as heat?

6.27 × 102 kJ

The enthalpy of fusion of ice is 6.020 kJ/mol. The heat capacity of liquid water is 75.4 J/mol·°C. What is the smallest number of ice cubes at 0°C, each containing one mole of water, necessary to cool 500 g of liquid water initially at 20°C to 0°C?

7

What is the specific heat capacity of a metal if it requires 178.1 J to change the temperature of 15.0 g of the metal from 25.00°C to 32.00°C?

1.70 J/g°C

A fuel-air mixture is placed in a cylinder fitted with a piston. The original volume is 0.310-L. When the mixture is ignited, gases are produced and 935 J of energy is released. To what volume will the gases expand against a constant pressure of 635 mmHg, if all the energy released is converted to work to push the piston?

11.4 L

How much heat is required to raise the temperature of a 5.75-g sample of iron (specific heat = 0.450 J/g°C) from 25.0°C to 79.8°C?

142 J

Of energy, work, enthalpy, and heat, how many are state functions?

2

The ΔH value for the reaction is -90.8 kJ. How much heat is released when 66.9 g Hg is reacted with oxygen?

30.3 kJ

You take 295.5 g of a solid at 30.0°C and let it melt in 425 g of water. The water temperature decreases from 85.1°C to 30.0°C. Calculate the heat of fusion of this solid.

331 J/g

The heat of combustion of benzene, C6H6, is -41.74 kJ/g. Combustion of 2.82 g of benzene causes a temperature rise of 3.29°C in a certain bomb calorimeter. What is the heat capacity of this bomb calorimeter?

35.8 kJ/°C

Consider the following specific heats of metals. Metal Specific Heat Zinc 0.387 J/(g°C) Magnesium 1.02 J/(g°C) Iron 0.450 J/(g°C) Silver 0.237 J/(g°C) Lead 0.127 J/(g°C) If the same amount of heat is added to 25.0 g of each of the metals, which are all at the same initial temperature, which metal will have the highest temperature?

Lead

According to the first law of thermodynamics, the energy of the universe is constant. Does this mean that ΔE is always equal to zero?

No, ΔE does not always equal zero because it refers to the system's internal energy, which is affected by heat and work.

Which statement is true of a process in which one mole of a gas is expanded from state A to state B?

The amount of heat released in the process will depend on the path taken.

In the lab, you mix two solutions (each originally at the same temperature) and the temperature of the resulting solution decreases. Which of the following is true?

The chemical reaction is absorbing energy.

A property that is independent of the pathway is called an intensive property.

false

The change in enthalpy can always be thought of as equal to energy flow as heat.

false

What is true about the value of ΔE?

It is equal to zero.

What is true about the value of ΔH?

It is equal to zero.

Which one of the following statements is false?

A bomb calorimeter measures ΔH directly.

Calculate the work for the expansion of CO2 from 1.0 to 4.7 liters against a pressure of 1.0 atm at constant temperature.

-3.7 L·atm

A gas absorbs 0.0 J of heat and then performs 30.7 J of work. The change in internal energy of the gas is

-30.7 J

What is the specific heat capacity of silver if it requires 86.3 J to raise the temperature of 15 grams of silver by 25°C?

0.23 J/g°C

A 140.0-g sample of water at 25.0°C is mixed with 111.7 g of a certain metal at 100.0°C. After thermal equilibrium is established, the (final) temperature of the mixture is 29.6°C. What is the specific heat capacity of the metal, assuming it is constant over the temperature range concerned?

0.34 J/g°C

Exactly 123.7 J will raise the temperature of 10.0 g of a metal from 25.0°C to 60.0°C. What is the specific heat capacity of the metal?

0.353 J/g°C

What is the enthalpy change when 49.4 mL of 0.430 M sulfuric acid reacts with 23.3 mL of 0.309 M potassium hydroxide?

-0.402 kJ

A bomb calorimeter has a heat capacity of 2.47 kJ/K. When a 0.109-g sample of ethylene (C2H4) was burned in this calorimeter, the temperature increased by 2.22 K. Calculate the energy of combustion for one mole of ethylene.

-1.41 × 103 kJ/mol

30.0 mL of pure water at 282 K is mixed with 50.0 mL of pure water at 306 K. What is the final temperature of the mixture?

297 K

Consider the following processes: 2A → (1/2)B + C ΔH1 = 5 kJ/mol (3/2)B + 4C → 2A + C + 3D ΔH2 = -15 kJ/mol E + 4A → C ΔH3 = 10 kJ/mol Calculate ΔH for: C → E + 3D

-10 kJ/mol

Consider the following processes: ΔH (kJ/mol) 3B → 2C + D -125. (1/2)A → B 150 E + A → D 350 Calculate ΔH for: B → E + 2C

-175 kJ/mol

When 0.236 mol of a weak base (A-) is reacted with excess HCl, 6.91 kJ of energy is released as heat. What is ΔH for this reaction per mole of A- consumed?

-29.3 kJ

Calculate the work associated with the expansion of a gas from 42.0 L to 79.0 L at a constant pressure of 14.0 atm.

-518 L·atm

How much heat is liberated at constant pressure when 2.35 g of potassium metal reacts with 5.68 mL of liquid iodine monochloride (d = 3.24 g/mL)? K(s) + ICl(l) → KCl(s) + KI(s) ΔH° = -740.71 kJ/mol

2.23 × 101 kJ

The total volume of hydrogen gas needed to fill the Hindenburg was 2.11 × 108 L at 1.00 atm and 24.7°C. How much energy was evolved when it burned?

2.47 × 109 kJ

A chunk of lead at 91.6°C was added to 200.0 g of water at 15.5°C. The specific heat of lead is 0.129 J/g°C, and the specific heat of water is 4.18 J/g°C. When the temperature stabilized, the temperature of the mixture was 17.9°C. Assuming no heat was lost to the surroundings, what was the mass of lead added?

211 g

A 32.5 g piece of aluminum (which has a molar heat capacity of 24.03 J/°C·mol) is heated to 82.4°C and dropped into a calorimeter containing water (specific heat capacity of water is 4.18 J/g°C) initially at 22.3°C. The final temperature of the water is 24.2°C. Ignoring significant figures, calculate the mass of water in the calorimeter.

212 g

One mole of an ideal gas is expanded from a volume of 1.00 liter to a volume of 8.93 liters against a constant external pressure of 1.00 atm. How much work (in joules) is performed on the surroundings? Ignore significant figures for this problem. (T = 300 K; 1 L·atm = 101.3 J)

803 J

Consider the reaction H2(g) + O2(g) → H2O(l) ΔH° = -286 kJ Which of the following is true?

Both A and C are true.

What is true about the value of q?

It is equal to zero.

What is true about the value of w?

It is equal to zero.

C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l), ΔH = -1.37 × 103 kJ For the combustion of ethyl alcohol as described in the above equation, which of the following is true? I. The reaction is exothermic. II. The enthalpy change would be different if gaseous water was produced. III. The reaction is not an oxidation-reduction one. IV. The products of the reaction occupy a larger volume than the reactants.

I. The reaction is exothermic. II. The enthalpy change would be different if gaseous water was produced.

Which of the following properties is (are) intensive properties? I. mass II. temperature III. volume IV. concentration V. energy

II and IV

Consider the reaction: C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l); ΔH = -1.37 × 103 kJ Consider the following propositions: I. The reaction is endothermic II. The reaction is exothermic. III. The enthalpy term would be different if the water formed was gaseous. Which of these propositions is (are) true?

II. The reaction is exothermic. III. The enthalpy term would be different if the water formed was gaseous.

Which of the following statements is/are true? I. q (heat) is a state function because ΔH is a state function and q = ΔH. II. When 50.0 g of aluminum at 20.0°C is placed in 50.0 mL of water at 30.0°C, the H2O will undergo a smaller temperature change than the aluminum. (The density of H2O = 1.0 g/mL, specific heat capacity of H2O = 4.18 J/g°C, specific heat capacity of aluminum = 0.89 J/g°C) III. When a gas is compressed, the work is negative since the surroundings are doing work on the system and energy flows out of the system. IV. For the reaction (at constant pressure) 2N2(g) + 5O2(g) → 2N2O5(g), the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps.

III. When a gas is compressed, the work is negative since the surroundings are doing work on the system and energy flows out of the system. IV. For the reaction (at constant pressure) 2N2(g) + 5O2(g) → 2N2O5(g), the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps.

A 45.9 g sample of a metal is heated to 95.2°C and then placed in a calorimeter containing 120.0 g of water (c = 4.18 J/g°C) at 21.6°C. The final temperature of the water is 24.5°C. Which metal was used?

Iron (c = 0.45 J/g°C)

Two metals of equal mass with different heat capacities are subjected to the same amount of heat. Which undergoes the smallest change in temperature?

The metal with the higher heat capacity.

On a cold winter day, a steel metal fence post feels colder than a wooden fence post of identical size because:

The specific heat capacity of steel is lower than the specific heat capacity of wood.

Which of the following statements is correct?

The system does work on the surroundings when an ideal gas expands against a constant external pressure.

For a particular process q = -17 kJ and w = 21 kJ. Which of the following statements is false?

The system does work on the surroundings.

Given the equation S(s) + O2(g) → SO2(g), ΔH = -296 kJ, which of the following statement(s) is (are) true? I. The reaction is exothermic. II. When 0.500 mole sulfur is reacted, 148 kJ of energy is released. III. When 32.0 g of sulfur are burned, 2.96 × 105 J of energy is released.

all are true

Which of the following statements correctly describes the signs of q and w for the following exothermic process at P = 1 atm and T = 370 K? H2O(g) → H2O(l)

q is negative, w is positive.

If 5.0 kJ of energy is added to a 15.5-g sample of water at 10.°C, the water

still a liquid

For the reaction H2O(l) → H2O(g) at 298 K and 1.0 atm, ΔH is more positive than ΔE by 2.5 kJ/mol. This quantity of energy can be considered to be

the work done in pushing back the atmosphere

A state function does not depend on the system's past or future.

true

In exothermic reaction, potential energy stored in chemical bonds is being converted to thermal energy via heat.

true

The specific heat capacities of metals are relatively low.

true

When a system performs work on the surroundings, the work is reported with a negative sign.

true

For a particular process q = 20 kJ and w = 15 kJ. Which of the following statements is true?

ΔE = 35 kJ

Consider the following numbered processes: 1. A → 2B 2. B → C + D 3. E → 2D ΔH for the process A → 2C + E is

ΔH1 + 2ΔH2 - ΔH3

If a student performs an endothermic reaction in a calorimeter, how does the calculated value of ΔH differ from the actual value if the heat exchanged with the calorimeter is not taken into account?

ΔHcalc would be less positive because the reaction absorbs heat from the calorimeter.