Deck 6: Principles of Chemical Reactivity: Energy and Chemical Reactions

Question 1

The energy associated with a stretched spring is called _____.

A) heat
B) internal energy
C) temperature
D) kinetic energy
E) potential energy

Answer 1

potential energy

Question 2

Exactly 149.6 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?

A) 0.427 J/(g · °C)
B) 2.34 J/(g · °C)
C) 20.6 J/(g · °C)
D) 35.8 J/(g · °C)
E) None of these

Answer 2

0.427 J/(g · °C)

Question 3

If 46.1 g of copper at 11.6 °C is placed in 85.0 g of water at 72.4 °C,what is the final temperature of the mixture? The specific heat capacities of copper and water are 0.385 J/g ⋅ K and 4.184 J/g ⋅ K,respectively.

A) 71.2 °C
B) 63.6 °C
C) 51.0 °C
D) 42.0 °C
E) 69.5 °C

Answer 3

69.5 °C

Question 4

How much energy is gained by copper when 68.4 g of copper is warmed from 13.4 °C to 78.4 °C? The specific heat capacity of copper is 0.385 J/(g·°C).

A) 3.53 × 10² J
B) 30.18 J
C) 25.02 J
D) 1.71 × 10³ J
E) 2.06 × 10³ J

Question 5

It is relatively easy to change the temperature of a substance that

A) is very massive.
B) is an insulator.
C) has a high specific heat capacity.
D) has a low specific heat capacity.
E) is brittle.

Question 6

Calculate the energy in the form of heat (in kJ)required to convert 325 grams of liquid water at 20.0 °C to steam at 115 °C.Assume that no energy in the form of heat is transferred to the environment.(Heat of fusion = 333 J/g; heat of vaporization = 2256 J/g; specific heat capacities: liquid water = 4.184 J/g⋅K,steam = 1.92 J/g⋅K)

A) 129 kJ
B) 121 kJ
C) 851 kJ
D) 914 kJ
E) 735 kJ

Question 7

Which of the following processes will result in the lowest final temperature of the metal-water mixture at when thermal equilibrium is reached? The specific heat capacity of iron is 0.449 J/(g·°C).The specific heat capacity of water is 4.184 J/(g·°C).

A) the addition of 100 g of iron at 95°C to 80 mL of water at 25°C in an insulated container
B) the addition of 100 g of iron at 95°C to 100 mL of water at 25°C in an insulated container
C) the addition of 100 g of iron at 95°C to 40 mL of water at 25°C in an insulated container
D) the addition of 100 g of iron at 95°C to 20 mL of water at 25°C in an insulated container
E) the addition of 100 g of iron at 95°C to 60 mL of water at 25°C in an insulated container

Question 8

How much energy is needed to convert 50.8 g of ice at 0.00 °C to liquid water at 75.0 °C? Specific heat capacity (ice)= 2.10 J/g °C
Specific heat capacity (liquid water)= 4.18 J/g °C
Heat of fusion = 333 J/g
Heat of vaporization = 2258 J/g

A) 15.9 kJ
B) 1.82 kJ
C) 24.9 kJ
D) 32.8 kJ
E) 131 kJ

Question 9

Which of these physical changes would require the release of energy?

A) freezing a liquid
B) boiling a liquid
C) melting a solid
D) all of these
E) none of these

Question 10

If 35.0 g H₂O at 22.7 °C is combined with 65.0 g H₂O at 87.5 °C,what is the final temperature of the mixture? The specific heat capacity of water is 4.184 J/g⋅K.

A) 25.1 °C
B) 45.4 °C
C) 50.8 °C
D) 64.8 °C
E) 48.9 °C

Question 11

Which one of the following statements is INCORRECT?

A) Energy is neither created nor destroyed in chemical reactions.
B) Kinetic energy is the energy that results from an object's position.
C) Exothermic processes transfer heat from the system into the surroundings.
D) Increasing the thermal energy of a gas increases the motion of its atoms.
E) Energy is the capacity to do work.

Question 12

Which of the following is an endothermic process?

A) work is done by the system on the surroundings
B) heat energy flows from the system to the surroundings
C) work is done on the system by the surroundings
D) heat energy is evolved by the system
E) none of the above

Question 13

A 18.6-g piece of gold (s = 0.129 J/(g·°C)),initially at 285.4°C,is added to 147.2 g of a liquid,initially at 27.9°C,in an insulated container.The final temperature of the metal-liquid mixture at equilibrium is 28.9°C.What is the identity of the liquid? Neglect the heat capacity of the container.

A) ethanol (s = 2.43 J/(g·°C))
B) water (s = 4.18 J/(g·°C))
C) methanol (s = 2.53 J/(g·°C))
D) acetone (s = 2.15 J/(g·°C))
E) hexane (s = 2.27 J/(g·°C))

Question 14

Heat capacity is defined as

A) the amount of heat required to raise the temperature of 1 gram of substance by 1 K.
B) the amount of heat required to raise the temperature of a substance by 1 K.
C) the amount of heat required to vaporize a solid or liquid.
D) the maximum amount of heat that a substance may absorb without decomposing.
E) 4.18 cal/g⋅K.

Question 15

The specific heat capacity of water(liquid)is 4.18 J/g⋅°C.What is the molar specific heat capacity of this substance? The molar mass of water is 18.01 g/mol.

A) 75.3 J/mol⋅°C
B) 0.232 J/mol⋅°C
C) 4.31 J/mol⋅°C
D) 4.18 J/mol⋅°C
E) 0.239 J/mol⋅°C

Question 16

When 66.0 g of an unknown metal at 28.5 °C is placed in 83.0 g H₂O at 78.5 °C,the water temperature decreases to 75.9 °C.What is the specific heat capacity of the metal? The specific heat capacity of water is 4.184 J/g⋅K.

A) 0.055 J/g⋅K
B) 0.29 J/g⋅K
C) 0.69 J/g⋅K
D) 0.18 J/g⋅K
E) 2.6 J/g⋅K

Question 17

If 50.0 g of benzene (C₆H₆)absorbs 2.71 kJ of energy in the form of heat at 25.0 °C,what is the final temperature of benzene? The specific heat capacity of benzene is 1.72 J/g ⋅ K.

A) 25.0 °C
B) 31.5 °C
C) 56.5 °C
D) 32.3 °C
E) 57.3 °C

Question 18

Specific heat capacity is

A) the quantity of heat needed to change the temperature of 1.00 g of a substance by 1 K.
B) the quantity of heat needed to change the temperature of 1.00 g of a substance by 4.184 K.
C) the capacity of a substance to gain or lose a 1.00 J of energy in the form of heat.
D) the temperature change undergone when 1.00 g of a substance absorbs 4.184 J.
E) the maximum amount of energy in the form of heat that 1.00 g of a substance may absorb without decomposing.

Question 19

A 170.0-g sample of metal at 83.00°C is added to 170.0 g of H₂O(l)at 15.00°C in an insulated container.The temperature rises to 18.16°C.Neglecting the heat capacity of the container,what is the specific heat capacity of the metal? The specific heat capacity of H₂O(l)is 4.18 J/(g·°C).

A) 4.18 J/(g·°C)
B) 85.6 J/(g·°C)
C) 0.204 J/(g·°C)
D) -0.204 J/(g·°C)
E) 20.5 J/(g·°C)

Question 20

Many homes are heated using natural gas.The combustion of natural gas converts

A) chemical potential energy to thermal energy.
B) thermal energy to mechanical energy.
C) mechanical energy to chemical potential.
D) electrostatic energy to mechanical energy.
E) gravitational energy to acoustic energy.

Question 21

The heat of vaporization of benzene,C₆H₆,is 30.7 kJ/mol at its boiling point of 80.1 °C.How much energy in the form of heat is required to vaporize 102 g benzene at its boiling point?

A) 0.302 kJ
B) 23.6 kJ
C) 24.2 kJ
D) 40.1 kJ
E) 3.14 × 10³ kJ

Question 22

Given the thermochemical equation 4AlCl₃(s)+ 3O₂(g)→ 2Al₂O₃(s)+ 6Cl₂(g); Δ_rH
= -529 kJ/mol-rxn
Find Δ_rH
For the following reaction. Al₂O₃(s)+ Cl₂(g)→ AlCl₃(s)+ O₂(g)

A) 88.2 kJ/mol-rxn
B) 264.5 kJ/mol-rxn
C) 529 kJ/mol-rxn
D) 176.3 kJ/mol-rxn
E) -176.3 kJ/mol-rxn

Question 23

The thermochemical equation for the combustion of methanol is given below. CH₃OH( )+ 3/2 O₂(g)→ CO₂(g)+ 2 H ₂O(g)
Δ_rH° = -638.7 kJ/mol-rxn
What is the enthalpy change for the combustion of 8.59 g of CH₃OH?

A) -171 kJ
B) -19.9 kJ
C) -2.38 × 10³ kJ
D) -5.49 × 10³ kJ
E) -1.76 × 10⁶ kJ

Question 24

Commercial cold packs consist of solid ammonium nitrate and water.NH₄NO₃ absorbs 25.69 kJ of heat per mole dissolved in water.In a coffee-cup calorimeter,5.60 g NH₄NO₃ is dissolved in 100.0 g of water at 22.0 °C.What is the final temperature of the solution? Assume that the solution has a specific heat capacity of 4.18 J/g⋅K.

A) 0.0 °C
B) 17.9 °C
C) 11.6 °C
D) -54.8 °C
E) 26.1 °C

Question 25

The thermochemical equation for the combustion of butane is givenn below. C₄H₁₀(g)+ 13/2 O₂(g)→ 4 CO₂(g)+ 5 H₂O( )
Δ_rH° = -2877 kJ/mol-rxn
What is the enthalpy change for the reaction below?
8 CO₂(g)+ 10 H₂O( )→ 2 C₄H₁₀(g)+ 13 O₂(g)

A) +1439 kJ/mol-rxn
B) +2877 kJ/mol-rxn
C) -5754 kJ/mol-rxn
D) -2877 kJ/mol-rxn
E) +5754 kJ/mol-rxn

Question 26

Calculate the energy in the form of heat (in kJ)required to change 76.9 g of liquid water at 25.2 °C to ice at -15.2 °C.Assume that no energy in the form of heat is transferred to the environment.(Heat of fusion = 333 J/g; heat of vaporization = 2256 J/g; specific heat capacities: ice = 2.06 J/g⋅K,liquid water = 4.184 J/g⋅K)

A) -13.0 kJ
B) -8.1 kJ
C) -36.1kJ
D) -33.7 kJ
E) -10.5 kJ

Question 27

The following reaction of iron oxide with aluminum is an exothermic reaction. Fe₂O₃(s)+ 2 Al(s)→ 2 Fe(s)+ Al₂O₃(s)
The reaction of 5.00 g of Fe₂O₃ with excess Al(s)evolves 26.6 kJ of energy in the form of heat.Calculate the enthalpy change per mole of Fe₂O₃.

A) -5.32 kJ/mol
B) -1.33 × 10² kJ/mol
C) -2.12 × 10⁴ kJ/mol
D) -2.12 × 10² kJ/mol
E) -8.50 × 10² kJ/mol

Question 28

44.0 g of ice at -20.0 °C is mixed with 325 g of water at 32.1 °C.Calculate the final temperature of the mixture.Assume that no energy in the form of heat is transferred to the environment.(Heat of fusion = 333 J/g; specific heat capacities: ice = 2.06 J/g⋅K,liquid water = 4.184 J/g⋅K)

A) -0.6 °C
B) 5.5 °C
C) 12.1 °C
D) 17.6 °C
E) 38.9 °C

Question 29

What is the change in internal energy of the system (ΔU)if 65 kJ of heat energy is evolved by the system and 62 kJ of work is done on the system for a certain process?

A) -3 kJ
B) -127 kJ
C) -65 kJ
D) 3 kJ
E) 127 kJ

Question 30

What is the minimum mass of ice at 0.0 °C that must be added to 1.00 kg of water to cool the water from 28.0 °C to 12.0 °C? (Heat of fusion = 333 J/g; specific heat capacities: ice = 2.06 J/g⋅K,liquid water = 4.184 J/g⋅K)

A) 175 g
B) 201 g
C) 244 g
D) 299 g
E) 1140 g

Question 31

CaO(s)reacts with water to form Ca(OH)₂(aq).If 6.50 g CaO is combined with 99.70 g H₂O in a coffee cup calorimeter,the temperature of the resulting solution increases from 21.7 °C to 43.1 °C.Calculate the enthalpy change for the reaction per mole of CaO.Assume that the specific heat capacity of the solution is 4.18 J/g⋅K.

A) -1.45 kJ/mol
B) -82.0 kJ/mol
C) -9.42 kJ/mol
D) -165 kJ/mol
E) -532 kJ/mol

Question 32

Hydrazine,N₂H₄,is a liquid used as a rocket fuel.It reacts with oxygen to yield nitrogen gas and water. N₂H₄( )+ O₂(g)→ N₂(g)+ 2 H₂O( )
The reaction of 6.50 g N₂H₄ evolves 126.2 kJ of heat.Calculate the enthalpy change per mole of hydrazine combusted.

A) -19.4 kJ/mol
B) -25.6 kJ/mol
C) -126 kJ/mol
D) -622 kJ/mol
E) -820.kJ/mol

Question 33

How much heat is liberated at constant pressure if 0.515 g of calcium carbonate reacts with 32.7 mL of 0.498 M hydrochloric acid? CaCO₃(s)+ 2HCl(aq)→ CaCl₂(aq)+ H₂O(l)+ CO₂(g); Δ_rH° = -15.2 kJ/mol-rxn

A) -0.0782 kJ
B) -0.202 kJ
C) -7.83 kJ
D) -0.124 kJ
E) -7.57 kJ

Question 34

At constant pressure and 25°C,what is Δ_rH° for the following reaction 2C₂H₆(g)+ 7O₂(g)→ 4CO₂(g)+ H₂O(l)
If the complete consumption of 22.7 g of C₂H₆ liberates -1178 kJ of heat energy?

A) -3120 kJ/mol-rxn
B) -1560 kJ/mol-rxn
C) -1780 kJ/mol-rxn
D) -889 kJ/mol-rxn
E) -788 kJ/mol-rxn

Question 35

What quantity,in moles,of hydrogen is consumed when 179.6 kJ of energy is evolved from the combustion of a mixture of H₂(g)and O₂(g)? H₂(g)+ O₂(g)→ H₂O(l); Δ_rH° = -285.8 kJ/mol-rxn

A) 0.6284 mol
B) 0.3142 mol
C) 1.591 mol
D) 1.628 mol
E) 0.3716 mol

Question 36

When 10.0 g of KOH is dissolved in 100.0 g of water in a coffee-cup calorimeter,the temperature rises from 25.18 °C to 47.53 °C.What is the enthalpy change per gram of KOH dissolved in the water? Assume that the solution has a specific heat capacity of 4.18 J/g ⋅ K.

A) -116 J/g
B) -934 J/g
C) -1.03 × 10³ J/g
D) -2.19 × 10³ J/g
E) -1.03 × 10⁴ J/g

Question 37

One statement of the first law of thermodynamics is that

A) the amount of work done on a system is dependent of the pathway.
B) the total work done on a system must equal the heat absorbed by the system.
C) the total work done on a system is equal in magnitude,but opposite in sign of the heat absorbed by the system.
D) the total energy change for a system is equal to the sum of the heat transferred to or from the system and the work done by or on the system.
E) in any chemical process the heat flow must equal the change in enthalpy.

Question 38

Which of the following thermodynamic quantities are state functions: heat (q),work (w),enthalpy change (ΔH),and/or internal energy change (ΔU)?

A) q only
B) w only
C) ΔH only
D) ΔU only
E) ΔH and ΔU

Question 39

If q = 39 kJ and w = -74 kJ for a certain process,it most likely _____.

A) requires a catalyst
B) is endothermic
C) occurs slowly
D) is exothermic
E) cannot occur

Question 40

Calculate ΔU of a gas for a process in which the gas absorbs 45 J of heat and does 11 J of work by expanding.

A) -34 J
B) 56 J
C) -56 J
D) 0 J
E) 34 J

Question 41

When 50.0 mL of 1.60 M of HCl(aq)is combined with 50.0 mL of 1.70 M of NaOH(aq)in a coffee-cup calorimeter,the temperature of the solution increases by 10.7°C.What is the change in enthalpy for this balanced reaction? HCl(aq)+ NaOH(aq)→ NaCl(aq)+ H₂O( )
Assume that the solution density is 1.00 g/mL and the specific heat capacity of the solution is 4.18 J/g⋅°C.

A) -55.8 kJ
B) 55.8 kJ
C) 52.5 kJ
D) -52.5 kJ
E) -27.1 kJ

Question 42

What is the overall chemical equation that results from the sum of the given steps? ​
2 C(s)+ 2 H₂O(g)→ 2 CO(g)+ 2 H₂(g)
CO(g)+ H₂O(g)→ CO₂(g)+ H₂(g)
CO(g)+ 3 H₂(g)→ CH₄(g)+ H₂O(g)
​

A) 2 C(s)+ 2 H₂O(g)→ CO₂(g)+ CH₄(g)
B) 2 C(s)+ 3 H₂O(g)→ CO(g)+ CO₂(g)+ 3 H₂(g)
C) 2 C(s)+ H₂O(g)+ H₂(g)→ CO(g)+ CH₄(g)
D) 2 CO(g)+ 2 H₂(g)→ CH₄(g)+ CO₂(g)
E) 2 C(s)+ CH₄(g)+ 3 H₂O(g)→ 3 CO(g)+ 5 H₂(g)

Question 43

Determine Δ_rH° for the following reaction,2 NH₃(g)+ 5/2 O₂(g)→ 2 NO(g)+ 3 H₂O(g).The thermochemical equations for the reaction are given below: N₂(g)+ O₂(g)→ 2 NO(g)
Δ_rH° = +180.8 kJ/mol-rxn
N₂(g)+ 3 H₂(g)→ 2 NH₃(g)
Δ_rH° = -91.8 kJ/mol-rxn
2 H₂(g)+ O₂(g)→ 2 H₂O(g)
Δ_rH° = -483.6 kJ/mol-rxn

A) -1178.2 kJ/mol-rxn
B) -452.8 kJ/mol-rxn
C) -394.6 kJ/mol-rxn
D) -211.0 kJ/mol-rxn
E) +1178.2 kJ/mol-rxn

Question 44

A chemical reaction in a bomb calorimeter evolves 3.86 kJ of energy in the form of heat.If the temperature of the bomb calorimeter increases by 4.17 K,what is the heat capacity of the calorimeter?

A) 3.87 × 10³ J/K
B) 311 J/K
C) 926 J/K
D) 1.8 × 10³ J/K
E) 1.61 × 10⁴ J/K

Question 45

Determine the standard enthalpy of formation of Fe₂O₃(s)given the thermochemical equations below. Fe(s)+ 3 H₂O( )→ Fe(OH)₃(s)+ 3/2 H₂(g)
Δ_rH° = +160.9 kJ/mol-rxn
H₂(g)+ 1/2 O₂(g)→ H₂O( )
Δ_rH° = -285.8 kJ/mol-rxn
Fe₂O₃(s)+ 3 H₂O( )→ 2 Fe(OH)₃(s)
Δ_rH° = +288.6 kJ/mol-rxn

A) -252.6 kJ/mol-rxn
B) +163.7 kJ/mol-rxn
C) -824.2 kJ/mol-rxn
D) +33.2 kJ/mol-rxn
E) + 890.6 kJ/mol-rxn

Question 46

A bomb calorimeter has a heat capacity of 2.47 kJ/K.When a 0.111-g sample of ethylene (C₂H₄)was burned in this calorimeter,the temperature increased by 2.26 K.Calculate the enthalpy change per mole of ethylene combusted.

A) -5.29 kJ/mol
B) -50.3 kJ/mol
C) -624 kJ/mol
D) -0.274 kJ/mol
E) -1.41 × 10³ kJ/mol

Question 47

Which of the following reactions corresponds to the thermochemical equation for the standard molar enthalpy of formation of solid zinc nitrate?

A) Zn²⁺(aq)+ 2NO₃^-(aq)→ Zn(NO₃)₂(s)
B) Zn(OH)₂(s)+ 2HNO₃(aq)→ Zn(NO₃)₂(s)+ 2H₂O( )
C) Zn(s)+ N₂(g)+ 3O₂(g)→ Zn(NO₃)₂(s)
D) Zn(s)+ 2HNO₃(aq)→ Zn(NO₃)₂(s)+ H₂(g)
E) Zn(s)+ 2N(g)+ 6O(g)→ Zn(NO₃)₂(s)

Question 48

Determine the heat of evaporation of carbon disulfide, CS₂( )→ CS₂(g)
Given the enthalpies of reaction below.
C(s)+ 2 S(s)→ CS₂( )
Δ_rH° = +89.4 kJ/mol-rxn
C(s)+ 2 S(s)→ CS₂(g)
Δ_rH° = +116.7 kJ/mol-rxn

A) -206.1 kJ
B) -27.3 kJ
C) +27.3 kJ
D) +206.1 kJ
E) +1.31 kJ

Question 49

Determine the standard enthalpy of formation of calcium carbonate from the thermochemical equations given below. Ca(OH)₂(s)→ CaO(s)+ H₂O( )
Δ_rH° = 65.2 kJ/mol-rxn
Ca(OH)₂(s)+ CO₂(g)→ CaCO₃(s)+ H₂O( )
Δ_rH° = −113.8 kJ/mol-rxn
C(s)+ O₂(g)→ CO₂(g)
Δ_rH° = −393.5 kJ/mol-rxn
2 Ca(s)+ O₂(g)→ 2 CaO(s)
Δ_rH° = −1270.2 kJ/mol-rxn

A) −1712.3 kJ/mol-rxn
B) −441.8 kJ/mol-rxn
C) −849.6 kJ/mol-rxn
D) −980.6 kJ/mol-rxn
E) −1207.6 kJ/mol-rxn

Question 50

In thermodynamics,a(n)________ is defined as the object,or collection of objects,being studied.The surroundings include everything else.

Question 51

Using the following thermochemical data: 2Sm(s)+ 6HF(g)→ 2SmF₃(s)+ 3H₂(g)
Δ_rH° = -1929.4 kJ/mol-rxn
2Sm(s)+ 6HCl(g)→ 2SmCl₃(s)+ 3H₂(g)
Δ_rH° = -1498.0 kJ/mol-rxn
Calculate Δ_rH° for the following reaction:
SmF₃(s)+ 3HCl(g)→ SmCl₃(s)+ 3HF(g)

A) -3427.4 kJ/mol-rxn
B) 431.4 kJ/mol-rxn
C) 215.7 kJ/mol-rxn
D) 862.8 kJ/mol-rxn
E) -1713.7 kJ/mol-rxn

Question 52

Acetylene,C₂H₂,is a gas used in welding.The molar enthalpy of combustion for acetylene is -2599 kJ.A mass of 0.338 g C₂H₂(g)is combusted in a bomb calorimeter.If the heat capacity of the calorimeter is 729 J/K and it contains 1.150 kg of water,what is the temperature increase of the bomb calorimeter? The specific heat capacity of water is 4.184 J/g⋅K and the molar mass of acetylene is 26.04 g/mol.

A) 1.59 K
B) 6.09 K
C) 7.01 K
D) 12.3 K
E) 18.0 K

Question 53

When 0.265 mol of a weak base (A^-)reacts with excess HCl,6.91 kJ of energy is released as heat.What is ΔH for this reaction per mole of A^- consumed?

A) -38.4 kJ/mol
B) -66.7 kJ/mol
C) -26.1 kJ/mol
D) 38.4 kJ/mol
E) 26.1 kJ/mol

Question 54

Determine the enthalpy change for the decomposition of calcium carbonate CaCO₃(s)→ CaO(s)+ CO₂(g)
Given the thermochemical equations below.
Ca(OH)₂(s)→ CaO(s)+ H₂O( )
Δ_rH° = 65.2 kJ/mol-rxn
Ca(OH)₂(s)+ CO₂(g)→ CaCO₃(s)+ H₂O( )
Δ_rH° = −113.8 kJ/mol-rxn
C(s)+ O₂(g)→ CO₂(g)
Δ_rH° = −393.5 kJ/mol-rxn
2 Ca(s)+ O₂(g)→ 2 CaO(s)
Δ_rH° = −1270.2 kJ/mol-rxn

A) +48.6 kJ/mol-rxn
B) +179.0 kJ/mol-rxn
C) +345.5 kJ/mol-rxn
D) +441.0 kJ/mol-rxn
E) +1711.7 kJ/mol-rxn

Question 55

A bomb calorimeter has a heat capacity of 2.47 kJ/K.When a 0.103-g sample of a certain hydrocarbon was burned in this calorimeter,the temperature increased by 2.14 K.Calculate the energy of combustion for 1 g of the hydrocarbon.

A) -5.29 J/g
B) J/g
C) -0.120 J/g
D) J/g
E) -0.540 J/g

Question 56

Combustion of 2.14 g of liquid benzene (C₆H₆)causes a temperature rise of 16.2 °C in a constant-pressure calorimeter that has a heat capacity of 5.53 kJ/°C.What is ΔH for the following reaction? C₆H₆(l)+ O₂(g)→ 6 CO₂(g)+ 3 H₂O( )

A) -89.5 kJ/mol-rxn
B) 41.8 kJ/mol-rxn
C) -41.8 kJ/mol-rxn
D) -3.27 × 10³ kJ/mol-rxn
E) 89.5 kJ/mol-rxn

Question 57

Which of the following chemical equations does not correspond to a standard molar enthalpy of formation?

A) Mg(s)+ C(s)+ 3/2 O₂(g)→ MgCO₃(s)
B) C(s)+ 1/2 O₂(g)→ CO(g)
C) N₂(g)+ O₂(g)→ 2 NO(g)
D) N₂(g)+ 2 O₂(g)→ N₂O₄(g)
E) H₂(g)+ 1/2 O₂(g)→ H₂O( )

Question 58

The heat required to convert a solid at its melting point to a liquid is called the heat of ________.

Question 59

Which of the following has zero standard enthalpy of formation at 25 °C?

A) Br(g)
B) Br₂(g)
C) Br₂(l)
D) Br(s)
E) Br₂(s)

Question 60

When 1 mole of Fe₂O₃(s)reacts with H₂(g)to form Fe(s)and H₂O(g)by the following reaction,98.8 kJ of energy is absorbed. Fe₂O₃(s)+ 3 H₂(g)→ 2 Fe(s)+ 3 H₂O(g) (A)
(B)
Is the reaction endothermic or exothermic,and which of the enthalpy diagrams above
Represents this reaction?

A) Endothermic; A
B) Endothermic; B
C) Exothermic; A
D) Exothermic; B
E) None of these

Question 61

Dry ice converts directly from a solid to a gas when heated.This process is called ________.

Question 62

Internal energy and enthalpy are state functions.What is meant by this statement?

Question 63

_____ is used to measure the energy evolved or absorbed as heat in a chemical or physical process.

A) Calorimetry
B) Polarimetry
C) Coulometry
D) Spectrometry
E) Colorimetry

Question 64

In a reaction,the values of ∆H and ∆U are always the same irrespective of the path taken to reach the products from reactants.

Question 65

Why are you at greater risk from being burned by steam at 100 °C than from liquid water at the same temperature?