Question 1

A system absorbs 21.6 kJ of heat while performing 6.9 kJ of work on the surroundings.If the initial internal energy,U,is 61.2 kJ,what is the final value of U?

Accepted Answer

A) 32.7 kJ 
B) 46.5 kJ 
C) 61.2 kJ 
D) 75.9 kJ 
E) 89.7 kJ 
A) 32.7 kJ 
B) 46.5 kJ 
C) 61.2 kJ 
D) 75.9 kJ 
E) 89.7 kJ

Question 2

A system delivers 1275 J of heat while the surroundings perform 854 J of work on it.What is ΔU of the system?

Accepted Answer

A) -2129 J 
B) -421 J 
C) +421 J 
D) +2129 J 
E) -1275 J 
A) -2129 J 
B) -421 J 
C) +421 J 
D) +2129 J 
E) -1275 J

Question 3

What law states that energy can be converted from one form to another,but cannot be created or destroyed?

Accepted Answer

A) universal law 
B) first law of thermodynamics 
C) law of mass conservation 
D) law of conservation of energy 
E) law of constant energy 
A) universal law 
B) first law of thermodynamics 
C) law of mass conservation 
D) law of conservation of energy 
E) law of constant energy

Question 4

A student used a bomb calorimeter to determine the heat of combustion of an unknown compound.If the student ignored the heat capacity of the bomb calorimeter,the heat capacity of the unknown compound would be _________ the accepted value.

Accepted Answer

A) greater than (i.e.,less negative) 
B) less than (i.e.,more negative) 
C) equal to 
A) greater than (i.e.,less negative) 
B) less than (i.e.,more negative) 
C) equal to

Question 5

The dissolution of barium hydroxide in water is an exothermic process.Which statement is correct?

Accepted Answer

A) The enthalpy of solid barium hydroxide plus pure water is less than that of the solution,at the same temperature. 
B) The enthalpy of solid barium hydroxide plus pure water is greater than that of the solution,at the same temperature. 
C) The enthalpy of solid barium hydroxide plus pure water is the same as that of the solution,at the same temperature. 
D) The temperature of the solution is lower than of the barium hydroxide and water before mixing. 
E) When barium hydroxide dissolves in water,the system does work on the surroundings. 
A) The enthalpy of solid barium hydroxide plus pure water is less than that of the solution,at the same temperature. 
B) The enthalpy of solid barium hydroxide plus pure water is greater than that of the solution,at the same temperature. 
C) The enthalpy of solid barium hydroxide plus pure water is the same as that of the solution,at the same temperature. 
D) The temperature of the solution is lower than of the barium hydroxide and water before mixing. 
E) When barium hydroxide dissolves in water,the system does work on the surroundings.

Question 6

Consider the following two representations of chemical reactions.Each sphere represents 1 mol of atoms.   What is ΔHºrxn for the following reaction? CS(g)+ O(g)→ CO(g)+ S(g)

Accepted Answer

A) -359 kJ/mol 
B) 1434 kJ/mol 
C) -7142 kJ/mol 
D) -1434 kJ/mol 
E) 7142 kJ/mol 
A) -359 kJ/mol 
B) 1434 kJ/mol 
C) -7142 kJ/mol 
D) -1434 kJ/mol 
E) 7142 kJ/mol

Question 7

How much heat is released if 7.15 g CaO(s)is added to 152 g of H2O(l)? CaO(s)+ H2O(l)→ Ca(OH)2(s)ΔH°rxn = -64.8 kJ/mol

Accepted Answer

A) 7.68 kJ 
B) 8.26 kJ 
C) 508 kJ 
D) 547 kJ 
E) 555 kJ 
A) 7.68 kJ 
B) 8.26 kJ 
C) 508 kJ 
D) 547 kJ 
E) 555 kJ

Question 8

A glass containing 200.0 g of H2O at 20.0°C was placed in a refrigerator.The water loses 11.7 kJ as it cools to a constant temperature.What is its new temperature? The specific heat of water is 4.184 J/g·°C.

Accepted Answer

A) 0.0°C 
B) 4.0°C 
C) 6.0°C 
D) 14.0°C 
E) 34.0°C 
A) 0.0°C 
B) 4.0°C 
C) 6.0°C 
D) 14.0°C 
E) 34.0°C

Question 9

What is ΔH°rxn for the following reaction? SiO2(s)+ 4HCl(g)→ SiCl4(g)+ 2H2O(g)
Substance ΔH°f(kJ/mol)
SiO2(s)-859.3
SiCl4(g)-662.8
HCl(g)-92.3
H2O(g)-241.8

Accepted Answer

A) -1856.2 kJ/mol 
B) -1372.6 kJ/mol 
C) -47.0 kJ/mol 
D) 82.1 kJ/mol 
E) 530.6 kJ/mol 
A) -1856.2 kJ/mol 
B) -1372.6 kJ/mol 
C) -47.0 kJ/mol 
D) 82.1 kJ/mol 
E) 530.6 kJ/mol

Question 10

If two solutions are mixed together in a container and the container "feels hot",then

Accepted Answer

A) the reaction is endothermic. 
B) the reaction is exothermic. 
C) the energy of the universe is increased. 
D) the energy of both the system and the surroundings is decreased. 
E) the energy of the system is increased. 
A) the reaction is endothermic. 
B) the reaction is exothermic. 
C) the energy of the universe is increased. 
D) the energy of both the system and the surroundings is decreased. 
E) the energy of the system is increased.

Question 11

An endothermic reaction causes the surroundings to

Accepted Answer

A) warm up. 
B) become acidic. 
C) condense. 
D) decrease in temperature. 
E) release CO2. 
A) warm up. 
B) become acidic. 
C) condense. 
D) decrease in temperature. 
E) release CO2.

Question 12

The combustion of pentane produces heat according to the following thermochemical equation. C5H12(l)+ 8O2(g)→ 5CO2(g)+ 6H2O(l)ΔH°rxn = -3510 kJ/mol
How many grams of CO2 is produced per 2.50 × 103 kJ of heat released?

Accepted Answer

A) 6.27 g 
B) 31.3 g 
C) 61.8 g 
D) 157 g 
E) 220 g 
A) 6.27 g 
B) 31.3 g 
C) 61.8 g 
D) 157 g 
E) 220 g

Question 13

For which of the substances below is ΔHof = 0?

Accepted Answer

A) O2(g) 
B) N2(l) 
C) Na(g) 
D) Xe(l) 
E) A and B 
A) O2(g) 
B) N2(l) 
C) Na(g) 
D) Xe(l) 
E) A and B

Question 14

For which reaction is ΔH approximately (or exactly)equal to ΔU?

Accepted Answer

A) H2(g)+ Br2(g)→ 2HBr(g) 
B) H2O(l)→ H2O(g) 
C) CaCO3(s)→ CaO(s)+ CO2(g) 
D) 2H(g)+ O(g)→ H2O(l) 
E) CH4(g)+ 2O2(g)→ CO2(g)+ 2H2O(l) 
A) H2(g)+ Br2(g)→ 2HBr(g) 
B) H2O(l)→ H2O(g) 
C) CaCO3(s)→ CaO(s)+ CO2(g) 
D) 2H(g)+ O(g)→ H2O(l) 
E) CH4(g)+ 2O2(g)→ CO2(g)+ 2H2O(l)

Question 15

Which is not a state function?

Accepted Answer

A) internal energy 
B) volume 
C) work 
D) pressure 
E) enthalpy 
A) internal energy 
B) volume 
C) work 
D) pressure 
E) enthalpy

Question 16

Chemical reactions in a bomb calorimeter occur at constant pressure.

Accepted Answer

A) True 
 B)False

Question 17

What is ΔH°rxn for the following reaction? NO2(g)+ CO(g)→ CO2(g)+ NO(g)
Substance ΔH°f(kJ/mol)
NO(g)+90.4
NO2(g)+33.85
CO(g)-110.5
CO2(g)-393.5

Accepted Answer

A) 339.6 kJ 
B) 379.8 kJ 
C) -226.5 kJ 
D) -339.6 kJ 
E) -379.8 kJ 
A) 339.6 kJ 
B) 379.8 kJ 
C) -226.5 kJ 
D) -339.6 kJ 
E) -379.8 kJ

Question 18

When 0.7521 g of benzoic acid was burned in a calorimeter containing 1000.g of water,a temperature rise of 3.60°C was observed.What is the heat capacity of the bomb calorimeter,excluding the water? The heat of combustion of benzoic acid is -26.42 kJ/g.

Accepted Answer

A) 15.9 kJ/°C 
B) 4.2 kJ/°C 
C) 5.5 kJ/°C 
D) 1.3 kJ/°C 
E) 752 kJ/°C 
A) 15.9 kJ/°C 
B) 4.2 kJ/°C 
C) 5.5 kJ/°C 
D) 1.3 kJ/°C 
E) 752 kJ/°C

Question 19

Your favorite candy bar,Gummy Beakers,contains 1.2 × 106 J of energy while your favorite soft drink,Bolt,contains 6.7 × 105 J.If you eat two packs of Gummy Beakers a day and drink 3 cans of Bolt,what percent of your 2000 Calorie daily food intake is left for broccoli,beans,beef,etc.? (1 cal = 4.184 J)

Accepted Answer

A) 53% 
B) 47% 
C) 27% 
D) 11% 
E) 0% 
A) 53% 
B) 47% 
C) 27% 
D) 11% 
E) 0%

Question 20

Two solutions (the system),each with a volume of 25.0 mL at 25.0°C,are mixed in a beaker.A reaction occurs between them,and the temperature rises to 35.0°C.After the products have equilibrated with the surroundings,the temperature is again 25.0°C and the total volume is 50.0 mL.No gases are involved in the reaction.Which relationship concerning the change from initial to final states (both at 25.0°C)is correct?

Accepted Answer

A) ΔU = 0 
B) ΔH = 0 
C) ΔU > 0 
D) q = 0 
E) W = 0 
A) ΔU = 0 
B) ΔH = 0 
C) ΔU > 0 
D) q = 0 
E) W = 0

Exam 5: Thermochemistry

A system absorbs 21.6 kJ of heat while performing 6.9 kJ of work on the surroundings.If the initial internal energy,U,is 61.2 kJ,what is the final value of U?

A system delivers 1275 J of heat while the surroundings perform 854 J of work on it.What is ΔU of the system?

What law states that energy can be converted from one form to another,but cannot be created or destroyed?

A student used a bomb calorimeter to determine the heat of combustion of an unknown compound.If the student ignored the heat capacity of the bomb calorimeter,the heat capacity of the unknown compound would be _________ the accepted value.

The dissolution of barium hydroxide in water is an exothermic process.Which statement is correct?

Consider the following two representations of chemical reactions.Each sphere represents 1 mol of atoms. What is ΔHºrxn for the following reaction? CS(g)+ O(g)→ CO(g)+ S(g)

How much heat is released if 7.15 g CaO(s)is added to 152 g of H2O(l)? CaO(s)+ H2O(l)→ Ca(OH)2(s)ΔH°rxn = -64.8 kJ/mol

A glass containing 200.0 g of H2O at 20.0°C was placed in a refrigerator.The water loses 11.7 kJ as it cools to a constant temperature.What is its new temperature? The specific heat of water is 4.184 J/g·°C.

What is ΔH°rxn for the following reaction? SiO2(s)+ 4HCl(g)→ SiCl4(g)+ 2H2O(g) Substance ΔH°f(kJ/mol) SiO2(s)-859.3 SiCl4(g)-662.8 HCl(g)-92.3 H2O(g)-241.8

If two solutions are mixed together in a container and the container "feels hot",then

An endothermic reaction causes the surroundings to

The combustion of pentane produces heat according to the following thermochemical equation. C5H12(l)+ 8O2(g)→ 5CO2(g)+ 6H2O(l)ΔH°rxn = -3510 kJ/mol How many grams of CO2 is produced per 2.50 × 103 kJ of heat released?

For which of the substances below is ΔHof = 0?

For which reaction is ΔH approximately (or exactly)equal to ΔU?

Which is not a state function?

Chemical reactions in a bomb calorimeter occur at constant pressure.

What is ΔH°rxn for the following reaction? NO2(g)+ CO(g)→ CO2(g)+ NO(g) Substance ΔH°f(kJ/mol) NO(g)+90.4 NO2(g)+33.85 CO(g)-110.5 CO2(g)-393.5

When 0.7521 g of benzoic acid was burned in a calorimeter containing 1000.g of water,a temperature rise of 3.60°C was observed.What is the heat capacity of the bomb calorimeter,excluding the water? The heat of combustion of benzoic acid is -26.42 kJ/g.

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Consider the following two representations of chemical reactions.Each sphere represents 1 mol of atoms. What is ΔHº_rxn for the following reaction? CS(g)+ O(g)→ CO(g)+ S(g)

How much heat is released if 7.15 g CaO(s)is added to 152 g of H₂O(l)? CaO(s)+ H₂O(l)→ Ca(OH)₂(s)ΔH°_rxn = -64.8 kJ/mol

A glass containing 200.0 g of H₂O at 20.0°C was placed in a refrigerator.The water loses 11.7 kJ as it cools to a constant temperature.What is its new temperature? The specific heat of water is 4.184 J/g·°C.

What is ΔH°_rxn for the following reaction? SiO₂(s)+ 4HCl(g)→ SiCl₄(g)+ 2H₂O(g) Substance ΔH°_f(kJ/mol) SiO₂(s)-859.3 SiCl₄(g)-662.8 HCl(g)-92.3 H₂O(g)-241.8

The combustion of pentane produces heat according to the following thermochemical equation. C₅H₁₂(l)+ 8O₂(g)→ 5CO₂(g)+ 6H₂O(l)ΔH°_rxn = -3510 kJ/mol How many grams of CO₂ is produced per 2.50 × 10³ kJ of heat released?

For which of the substances below is ΔH^o_f = 0?

What is ΔH°_rxn for the following reaction? NO₂(g)+ CO(g)→ CO₂(g)+ NO(g) Substance ΔH°_f(kJ/mol) NO(g)+90.4 NO₂(g)+33.85 CO(g)-110.5 CO₂(g)-393.5