Question 1

How much heat is required to raise the temperature of 1500 g of water from 25°C to 52°C? The specific heat of water is 4.184 J/g·°C.

Accepted Answer

A) 1500 kJ 
B) 170 kJ 
C) 6.3 kJ 
D) 41 J 
E) 41 kJ 
A) 1500 kJ 
B) 170 kJ 
C) 6.3 kJ 
D) 41 J 
E) 41 kJ

Question 2

A piece of copper with a mass of 218 g has a heat capacity of 83.9 J/°C.What is the specific heat of copper?

Accepted Answer

A) 0.385 J/g·°C 
B) 1.83 × 104 J/g·°C 
C) 2.60 J/g·°C 
D) 1.32 J/g·°C 
E) 24.5 J/g·°C 
A) 0.385 J/g·°C 
B) 1.83 × 104 J/g·°C 
C) 2.60 J/g·°C 
D) 1.32 J/g·°C 
E) 24.5 J/g·°C

Question 3

Suppose a 50-g block of silver (specific heat = 0.2350 J/g·°C)at 100°C is placed in contact with a 50-g block of iron (specific heat = 0.4494 J/g·°C)at 0°C,and the two blocks are insulated from the rest of the universe.The final temperature of the two blocks

Accepted Answer

A) will be higher than 50°C. 
B) will be lower than 50°C. 
C) will be exactly 50°C. 
D) is unrelated to the composition of the blocks. 
E) cannot be predicted. 
A) will be higher than 50°C. 
B) will be lower than 50°C. 
C) will be exactly 50°C. 
D) is unrelated to the composition of the blocks. 
E) cannot be predicted.

Question 4

Calculate the standard enthalpy change for the reaction 2C8H18(l)+ 21O2(g)→ 8CO(g)+ 8CO2(g)+ 18H2O(l).Given:
2C8H18(l)+ 25O2(g)→ 16CO2(g)+ 18H2O(l)
ΔH° = -11,020.kJ/mol
2CO(g)+ O2(g)→ 2CO2(g)
ΔH° = -566.0 kJ/mol

Accepted Answer

A) 1.0454 × 104 kJ/mol 
B) -8756 kJ/mol 
C) 1.1586 × 104 kJ/mol 
D) -6492 kJ/mol 
E) -1.0454 × 104 kJ/mol 
A) 1.0454 × 104 kJ/mol 
B) -8756 kJ/mol 
C) 1.1586 × 104 kJ/mol 
D) -6492 kJ/mol 
E) -1.0454 × 104 kJ/mol

Question 5

In an endothermic process,heat is absorbed by the system.

Accepted Answer

A) True 
 B)False

Question 6

Which of the following has a standard enthalpy of formation value (ΔH°f)of zero at 298 K?

Accepted Answer

A) H2O(g) 
B) O(g) 
C) H2O(l) 
D) O2(g) 
E) O3(g) 
A) H2O(g) 
B) O(g) 
C) H2O(l) 
D) O2(g) 
E) O3(g)

Question 7

What is the equation for the formation reaction for gaseous hydrazine,N2H4,at 25ºC and 1 atm pressure?

Accepted Answer

A) 2N2H4(g)→ 2NH3(g)+ H2(g) 
B) 2NH3(g)+ H2(g)→ N2H4(g) 
C) N2(g)+ 2H2O(g)→ N2H4(g)+ O2(g) 
D) N2(g)+2H2(g)→ N2H4(g) 
E) 2NO2(g)+ 6H2(g)→ N2H4(g)+ 4H2O(g) 
A) 2N2H4(g)→ 2NH3(g)+ H2(g) 
B) 2NH3(g)+ H2(g)→ N2H4(g) 
C) N2(g)+ 2H2O(g)→ N2H4(g)+ O2(g) 
D) N2(g)+2H2(g)→ N2H4(g) 
E) 2NO2(g)+ 6H2(g)→ N2H4(g)+ 4H2O(g)

Question 8

How much heat is evolved if 0.600 kg of SO2 is burned in excess oxygen? 2SO2(g)+ O2(g)→ 2SO3(g)ΔH°rxn = -198 kJ/mol

Accepted Answer

A) 5.46 × 10-2 kJ 
B) 927 kJ 
C) 1.85 × 103 kJ 
D) 59,400 kJ 
E) 3.71 × 103 kJ 
A) 5.46 × 10-2 kJ 
B) 927 kJ 
C) 1.85 × 103 kJ 
D) 59,400 kJ 
E) 3.71 × 103 kJ

Question 9

The specific heat of gold is 0.129 J/g·°C.What is the molar heat capacity of gold?

Accepted Answer

A) 0.0394 J/mol·°C 
B) 0.129 J/mol·°C 
C) 25.4 J/mol·°C 
D) 39.4 kJ/mol·°C 
E) 197 J/mol·°C 
A) 0.0394 J/mol·°C 
B) 0.129 J/mol·°C 
C) 25.4 J/mol·°C 
D) 39.4 kJ/mol·°C 
E) 197 J/mol·°C

Question 10

Which equation has a ΔHrxn that is not equal to ΔHof of the product?

Accepted Answer

A) O2(g)+ H2(g)→ H2O2(g) 
B) ½O2(g)+ H2(g)→ H2O(g) 
C) H2(g)+ ½O2(g)+ → H2O(l) 
D) NO(g)+ ½O2(g)→ NO2(l) 
E) ½H2(g)+ ½Cl2(g)→ HCl(g) 
A) O2(g)+ H2(g)→ H2O2(g) 
B) ½O2(g)+ H2(g)→ H2O(g) 
C) H2(g)+ ½O2(g)+ → H2O(l) 
D) NO(g)+ ½O2(g)→ NO2(l) 
E) ½H2(g)+ ½Cl2(g)→ HCl(g)

Question 11

How much heat is required to raise the temperature of 12.0 g of water from 15.4°C to 93.0°C? The specific heat of water is 4.184 J/g·°C.

Accepted Answer

A) 223 J 
B) 773 J 
C) 503 J 
D) 4.67 ×103 J 
E) 3.90 ×103 J 
A) 223 J 
B) 773 J 
C) 503 J 
D) 4.67 ×103 J 
E) 3.90 ×103 J

Question 12

When 0.560 g of Na(s)reacts with excess F2(g)to form NaF(s),13.8 kJ of heat is evolved at standard-state conditions.What is the standard enthalpy of formation (ΔH°f)of NaF(s)?

Accepted Answer

A) 567 kJ/mol 
B) -24.8 kJ/mol 
C) -7.8 kJ/mol 
D) 24.8 kJ/mol 
E) -567 kJ/mol 
A) 567 kJ/mol 
B) -24.8 kJ/mol 
C) -7.8 kJ/mol 
D) 24.8 kJ/mol 
E) -567 kJ/mol

Question 13

Using Hess's law,what is ΔH°rxn for the following reaction? NO(g)+ O(g)→ NO2(g)
NO(g)+ O3(g)→ NO2(g)+O2(g)ΔH°rxn = -198.8 kJ/mol
O3(g)→ 3/2 O2(g)ΔH°rxn = -142.2 kJ/mol
O2(g)→ 2O(g)ΔH°rxn = +498.8 kJ/mol

Accepted Answer

A) -839.8 kJ/mol 
B) -306.0 kJ/mol 
C) 157.9 kJ/mol 
D) 394.9 kJ/mol 
E) 442.3 kJ/mol 
A) -839.8 kJ/mol 
B) -306.0 kJ/mol 
C) 157.9 kJ/mol 
D) 394.9 kJ/mol 
E) 442.3 kJ/mol

Question 14

Benzene is a starting material in the synthesis of nylon fibers and polystyrene (styrofoam).Its specific heat capacity is 1.74 J/g·°C.If 16.7 kJ of energy is absorbed by a 225-g sample of benzene at 20.0°C,what is its final temperature?

Accepted Answer

A) -22.7°C 
B) 37.7°C 
C) 42.7°C 
D) 62.7°C 
E) 80.1°C 
A) -22.7°C 
B) 37.7°C 
C) 42.7°C 
D) 62.7°C 
E) 80.1°C

Question 15

The heat absorbed by a system at constant pressure is equal to ΔU + PΔV.

Accepted Answer

A) True 
 B)False

Question 16

What is ΔH°rxn for the following reaction? H3AsO4(aq)+ 4H2(g)→ AsH3(g)+ 4H2O(l)
Substance ΔH°f(kJ/mol)
AsH3(g)171.5
H3AsO4(aq)-904.6
H2O(l)-285.8

Accepted Answer

A) -1876.3 kJ/mol 
B) -1018.9 kJ/mol 
C) -790.3 kJ/mol 
D) -410.1 kJ/mol 
E) -67.1 kJ/mol 
A) -1876.3 kJ/mol 
B) -1018.9 kJ/mol 
C) -790.3 kJ/mol 
D) -410.1 kJ/mol 
E) -67.1 kJ/mol

Question 17

Which represents the formation reaction for XeF4(g)? Each sphere represents 1 mol of atoms.

Accepted Answer

A)    
B)    
C)    
D)    
A)    
B)    
C)    
D)

Question 18

A common laboratory reaction is the neutralization of an acid with a base.When 50.0 mL of 0.500 M HCl at 25.0°C is added to 50.0 mL of 0.500 M NaOH at 25.0°C in a coffee cup calorimeter,the temperature of the mixture rises to 28.2°C.What is the heat of reaction per mole of acid? Assume the mixture has a specific heat capacity of 4.18 J/g·°C and that the densities of the reactant solutions are both 1.00 g/mL.

Accepted Answer

A) 670 J 
B) 1300 J 
C) 27 kJ 
D) 54 kJ 
E) > 100 kJ 
A) 670 J 
B) 1300 J 
C) 27 kJ 
D) 54 kJ 
E) > 100 kJ

Question 19

A home aquarium is an example of an open system.

Accepted Answer

A) True 
 B)False

Question 20

Suppose a new metallic element X is discovered,and its reactions with oxygen gas and chlorine gas at 298 K are studied. Trial
Reaction
ΔHºrxn (kJ/mol)
1
4X(s)+ 3O2(g)→ 2X2O3(s)
-600
2
2X(s)+ 3Cl2(g)→ 2XCl3(s)
-800
3
4XCl3(s)+ 3O2(g)→X2O3(s)+6Cl2(g)
-200
However,it is later discovered that one of the samples was contaminated,and the ΔHºrxn value from this trial is not reliable.Which trial had the contaminated sample,and what should the correct value of ΔHºrxn be for this trial?

Accepted Answer

A) Trial 1 had the contaminated sample; its ΔHºrxn value should be -900 kJ/mol. 
B) Trial 2 had the contaminated sample; its ΔHºrxn value should be +100 kJ/mol. 
C) Trial 3 had the contaminated sample; its ΔHºrxn value should be -1000 kJ/mol. 
D) Trial 3 had the contaminated sample; its ΔHºrxn value should be +1000 kJ/mol. 
E) Not enough information is provided; all three trials must be redone. 
A) Trial 1 had the contaminated sample; its ΔHºrxn value should be -900 kJ/mol. 
B) Trial 2 had the contaminated sample; its ΔHºrxn value should be +100 kJ/mol. 
C) Trial 3 had the contaminated sample; its ΔHºrxn value should be -1000 kJ/mol. 
D) Trial 3 had the contaminated sample; its ΔHºrxn value should be +1000 kJ/mol. 
E) Not enough information is provided; all three trials must be redone.

Exam 5: Thermochemistry

How much heat is required to raise the temperature of 1500 g of water from 25°C to 52°C? The specific heat of water is 4.184 J/g·°C.

A piece of copper with a mass of 218 g has a heat capacity of 83.9 J/°C.What is the specific heat of copper?

Suppose a 50-g block of silver (specific heat = 0.2350 J/g·°C)at 100°C is placed in contact with a 50-g block of iron (specific heat = 0.4494 J/g·°C)at 0°C,and the two blocks are insulated from the rest of the universe.The final temperature of the two blocks

Calculate the standard enthalpy change for the reaction 2C8H18(l)+ 21O2(g)→ 8CO(g)+ 8CO2(g)+ 18H2O(l).Given: 2C8H18(l)+ 25O2(g)→ 16CO2(g)+ 18H2O(l) ΔH° = -11,020.kJ/mol 2CO(g)+ O2(g)→ 2CO2(g) ΔH° = -566.0 kJ/mol

In an endothermic process,heat is absorbed by the system.

Which of the following has a standard enthalpy of formation value (ΔH°f)of zero at 298 K?

What is the equation for the formation reaction for gaseous hydrazine,N2H4,at 25ºC and 1 atm pressure?

How much heat is evolved if 0.600 kg of SO2 is burned in excess oxygen? 2SO2(g)+ O2(g)→ 2SO3(g)ΔH°rxn = -198 kJ/mol

The specific heat of gold is 0.129 J/g·°C.What is the molar heat capacity of gold?

Which equation has a ΔHrxn that is not equal to ΔHof of the product?

How much heat is required to raise the temperature of 12.0 g of water from 15.4°C to 93.0°C? The specific heat of water is 4.184 J/g·°C.

When 0.560 g of Na(s)reacts with excess F2(g)to form NaF(s),13.8 kJ of heat is evolved at standard-state conditions.What is the standard enthalpy of formation (ΔH°f)of NaF(s)?

Using Hess's law,what is ΔH°rxn for the following reaction? NO(g)+ O(g)→ NO2(g) NO(g)+ O3(g)→ NO2(g)+O2(g)ΔH°rxn = -198.8 kJ/mol O3(g)→ 3/2 O2(g)ΔH°rxn = -142.2 kJ/mol O2(g)→ 2O(g)ΔH°rxn = +498.8 kJ/mol

Benzene is a starting material in the synthesis of nylon fibers and polystyrene (styrofoam).Its specific heat capacity is 1.74 J/g·°C.If 16.7 kJ of energy is absorbed by a 225-g sample of benzene at 20.0°C,what is its final temperature?

The heat absorbed by a system at constant pressure is equal to ΔU + PΔV.

What is ΔH°rxn for the following reaction? H3AsO4(aq)+ 4H2(g)→ AsH3(g)+ 4H2O(l) Substance ΔH°f(kJ/mol) AsH3(g)171.5 H3AsO4(aq)-904.6 H2O(l)-285.8

Which represents the formation reaction for XeF4(g)? Each sphere represents 1 mol of atoms.

A home aquarium is an example of an open system.

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Calculate the standard enthalpy change for the reaction 2C₈H₁₈(l)+ 21O₂(g)→ 8CO(g)+ 8CO₂(g)+ 18H₂O(l).Given: 2C₈H₁₈(l)+ 25O₂(g)→ 16CO₂(g)+ 18H₂O(l) ΔH° = -11,020.kJ/mol 2CO(g)+ O₂(g)→ 2CO₂(g) ΔH° = -566.0 kJ/mol

Which of the following has a standard enthalpy of formation value (ΔH°_f)of zero at 298 K?

What is the equation for the formation reaction for gaseous hydrazine,N₂H₄,at 25ºC and 1 atm pressure?

How much heat is evolved if 0.600 kg of SO₂ is burned in excess oxygen? 2SO₂(g)+ O₂(g)→ 2SO₃(g)ΔH°_rxn = -198 kJ/mol

Which equation has a ΔH_rxn that is not equal to ΔH^o_f of the product?

When 0.560 g of Na(s)reacts with excess F₂(g)to form NaF(s),13.8 kJ of heat is evolved at standard-state conditions.What is the standard enthalpy of formation (ΔH°_f)of NaF(s)?

Using Hess's law,what is ΔH°_rxn for the following reaction? NO(g)+ O(g)→ NO₂(g) NO(g)+ O₃(g)→ NO₂(g)+O₂(g)ΔH°_rxn = -198.8 kJ/mol O₃(g)→ 3/2 O₂(g)ΔH°_rxn = -142.2 kJ/mol O₂(g)→ 2O(g)ΔH°_rxn = +498.8 kJ/mol

What is ΔH°_rxn for the following reaction? H₃AsO₄(aq)+ 4H₂(g)→ AsH₃(g)+ 4H₂O(l) Substance ΔH°_f(kJ/mol) AsH₃(g)171.5 H₃AsO₄(aq)-904.6 H₂O(l)-285.8

Which represents the formation reaction for XeF₄(g)? Each sphere represents 1 mol of atoms.