Deck 13: Energy and Thermochemistry

Question 1

Thermodynamics is the study of systems on the microscopic scale. It explains the interrelation of energy and chemistry and relies on information about individual molecular properties to do this.

Answer 1

False

Question 2

Energy generated by a chemical reaction can be transferred as a result of motion against an opposing force as ____. .

Answer 2

work

Question 3

Match the system name to its short description.
-Both matter and energy can be exchanged with its surroundings

A) Open
B) Closed
C) Isolated

Answer 3

A

Question 4

Match the system name to its short description.
-Only energy can be exchanged with its surroundings

A) Open
B) Closed
C) Isolated

Question 5

Match the system name to its short description.
-Neither energy or matter can be exchanged with its surroundings

A) Open
B) Closed
C) Isolated

Question 6

What type of system is the Earth and its atmosphere?

A) Open.
B) Closed.
C) Isolated.
D) Not possible to define as a system.

Question 7

What type of system is the Atlantic ocean?

A) Open.
B) Closed.
C) Isolated.
D) Not possible to define as a system.

Question 8

The term heat capacity, C, is used to quantify heat changes; it can be defined in different ways. Match the short definition with the correct heat capacity symbol.
-Specific heat capacity is the heat needed to raise the temperature of 1 gram of substance by 1 K

A) C_s
B) C_m
C) C_p
D) C_v

Question 9

The term heat capacity, C, is used to quantify heat changes; it can be defined in different ways. Match the short definition with the correct heat capacity symbol.
-Molar heat capacity is the heat needed to raise the temperature of 1 mol of substance by 1 K

A) C_s
B) C_m
C) C_p
D) C_v

Question 10

The term heat capacity, C, is used to quantify heat changes; it can be defined in different ways. Match the short definition with the correct heat capacity symbol.
-Molar heat capacity is the heat needed to raise the temperature of 1 mol of substance by 1 K, for a gas, measured at constant pressure

A) C_s
B) C_m
C) C_p
D) C_v

Question 11

The term heat capacity, C, is used to quantify heat changes; it can be defined in different ways. Match the short definition with the correct heat capacity symbol.
-Molar heat capacity is the heat needed to raise the temperature of 1 mol of substance by 1 K, for a gas, measured at constant volume

A) C_s
B) C_m
C) C_p
D) C_v

Question 12

The molar heat capacity, C_m of gold (Au(s)) is 25.4 J K^-1 mol^-1. Calculate the energy (in J) required to heat a 100 g bar of gold from 25 °C to 75 °C?

A) Not possible to calculate.
B) 645.
C) 127000.
D) 1.

Question 13

The specific heat capacity of liquid water is 4.18 J K^-1 g^-1. Calculate the temperature rise (in K) when 1050 J of heat is transferred to 5 mol of water.

A) 2.79
B) 50.24
C) 48.73
D) 2.79 × 10^-3.

Question 14

The specific heat capacity of Cu (s) is 0.38 J K^-1 g^-1 and that of Au (s) is 0.129 J K^-1 g^-1. When 100 J of heat is added to 100 g of sample of each of these substances, will one experience a larger increase in temperature?

A) Yes, gold.
B) No.
C) Yes, copper.
D) Not enough energy to increase the temperature of either substance.

Question 15

The specific heat capacity of iron (Fe(s)) is 0.45 J K^-1 g^-1, how much energy ( in J) must be added to raise the temperature of a 250 g iron bar by 30 ° C?

A) 34.104.
B) 34104.
C) 3375.
D) 6 × 10^-5.

Question 16

Match the definition with the quantity it is describing.
-

A) Energy required to melt one mol of a pure substance at its melting point, T_m, at 1 bar pressure
B) Energy required to vaporize one mole of a pure liquid at its boiling point, T_b, at 1 bar pressure
C) Enthalpy change at 298 K when 1 mol of a compound is formed under standard conditions from its constituent elements in their standard states
D) Enthalpy change when 1 mol of a substance reacts completely with oxygen gas at 1 bar pressure

Question 17

Match the definition with the quantity it is describing.
-

A) Energy required to melt one mol of a pure substance at its melting point, T_m, at 1 bar pressure
B) Energy required to vaporize one mole of a pure liquid at its boiling point, T_b, at 1 bar pressure
C) Enthalpy change at 298 K when 1 mol of a compound is formed under standard conditions from its constituent elements in their standard states
D) Enthalpy change when 1 mol of a substance reacts completely with oxygen gas at 1 bar pressure

Question 18

Match the definition with the quantity it is describing.
-

A) Energy required to melt one mol of a pure substance at its melting point, T_m, at 1 bar pressure
B) Energy required to vaporize one mole of a pure liquid at its boiling point, T_b, at 1 bar pressure
C) Enthalpy change at 298 K when 1 mol of a compound is formed under standard conditions from its constituent elements in their standard states
D) Enthalpy change when 1 mol of a substance reacts completely with oxygen gas at 1 bar pressure

Question 19

Match the definition with the quantity it is describing.
-

A) Energy required to melt one mol of a pure substance at its melting point, T_m, at 1 bar pressure
B) Energy required to vaporize one mole of a pure liquid at its boiling point, T_b, at 1 bar pressure
C) Enthalpy change at 298 K when 1 mol of a compound is formed under standard conditions from its constituent elements in their standard states
D) Enthalpy change when 1 mol of a substance reacts completely with oxygen gas at 1 bar pressure

Question 20

The standard enthalpy change of formation is the energy released when 1 mol of compound is formed from its constituent elements under which set of conditions?

A) Elements in their standard states and 1 bar pressure.
B) Elements in their standard states and 1 atm pressure.
C) Elements in their standard states at 101325 Pa pressure.
D) Elements in their standard states at any temperature and pressure.

Question 21

The standard enthalpy change of fusion and vaporization for water are +6.01 kJ mol^-1 and +40.7 kJ mol^-1 respectively. Why is the value for vaporization so much larger than fusion?

A) Because it is measured at a higher temperature.
B) Because the pressure has increased.
C) Because gas is released into the surroundings.
D) Because overcoming all intermolecular forces that hold a liquid together needs a lot of energy.

Question 22

The standard enthalpy change of vaporization of water is + 40.7 kJ mol^-1. Calculate the enthalpy change (in kJ) when 15 g of water vaporizes at its boiling point at 1 bar.

A) 611.
B) 49.
C) + 34.
D) 3.

Question 23

Calculate the enthalpy change (in kJ mol^-1) when 1 mol of solid ethanol is melted at 155.8 K and heated to 298 K. (Take the molar heat capacity of liquid ethanol to be 112 J K^-1 mol^-1), (ethanol) = + 4.60 kJ mol^-1 and (ethanol) = + 43.5 kJ mol^-1.

A) + 64.0
B) + 20.5
C) + 15.9
D) + 38

Question 24

Calculate the standard enthalpy change (in kJ mol^-1) for the hydrogenation of propene to propane at 298 K. The standard enthalpy change at 298 K for reactions of graphite and hydrogen gas to form 1 mol of each of these compounds is + 20.4 kJ mol^-1 and - 103.9 kJ mol^-1 respectively.

A) + 83.5
B) + 124.3
C) - 83.5
D) - 124.3

Question 25

Calculate the standard enthalpy change (in kJ mol^-1) for the hydrogenation of ethyne to ethene at 298 K. The standard enthalpy change at 298 K for reactions of graphite and hydrogen gas to form 1 mol of each of these compounds is + 226.7 kJ mol^-1 and + 52.5 kJ mol^-1 respectively.

A) + 279.2
B) - 279.2
C) + 174.2
D) - 174.2

Question 26

Calculate the enthalpy change at 298.15 K and 1 bar pressure for the following reaction, using data in Appendix 7:
SiCl₄ (l) + 2H₂O (l) → SiO₂ (s) + 4 HCl (g)

A) + 30.4 kJ mol^-1.
B) - 30.4 kJ mol^-1.
C) + 21.5 kJ mol^-1.
D) - 21.5 kJ mol^-1.

Question 27

Calculate the enthalpy change at 298.15 K and 1 bar pressure for the following reaction, using data in Appendix 7:
CH₄ (g) + Cl₂ (g) → CH₃Cl (g) + HCl (g)

A) - 101.2 kJ mol^-1.
B) + 101.2 kJ mol^-1.
C) - 250.8 kJ mol^-1.
D) 250.8 kJ mol^-1.

Question 28

Calculate the enthalpy change at 298.15 K and 1 bar pressure for the following reaction, using data in Appendix 7:
2 Cl (g) → Cl₂ (g)

A) - 121.7 kJ mol^-1.
B) 0 kJ mol^-1.
C) - 243.4 kJ mol^-1.
D) + 243.4 kJ mol^-1.

Question 29

Calculate the enthalpy change 298.15 K and 1 bar pressure for the following reaction, using data in Appendix 7:
NH₃ (g) + HNO₃ (l) → NH₄NO₃ (s)

A) + 585.8 kJ mol^-1.
B) + 145.4 kJ mol^-1.
C) - 585.8 kJ mol^-1.
D) - 145.4 kJ mol^-1.

Question 30

The symbol conveys which of the following information? Select all that apply.

A) Standard enthalpy change of combustion.
B) Standard enthalpy change measured at 273.15 K.
C) Enthalpy change measured at 1 bar pressure.
D) Enthalpy change measured for 1 gram of substance.

Question 31

The combustion of glucose (C₆H₁₂O₆) at 1 bar and 298 K releases 2802.5 kJ mol^-1 of heat.
C₆H₁₂O₆ (s) + 6 O₂ (g) $\rightarrow$ 6 CO₂ (g) + 6 H₂O (l) Calculate the standard enthalpy change of formation of glucose (in kJ mol^-1). Use $\Delta_{\mathrm{f}} H_{208}^{\circ}$ data in Appendix 7.

A) + 2123.2
B) - 1273.3
C) + 1273.3
D) - 6878.3

Question 32

The combustion of ethanol (C₂H₅OH) at 1 bar and 298 K releases 1367 kJ mol^-1 of heat.
C₂H₅OH (l) + 3 O₂ (g) $\rightarrow$ 2 CO₂ (g) + 3 H₂O (l) Calculate the standard enthalpy change of formation of ethanol (in kJ mol^-1). Use $\Delta_{\mathrm{f}} H_{208}^{\circ}$ data in Appendix 7.

A) - 277.4
B) + 277.4
C) - 3011.4
D) + 3011.4

Question 33

Values of bond dissociation enthalpies D_(A-B) are always positive because they are measured in the gas phase.

Question 34

Calculate $\Delta_{\mathrm{T}} H$ for the following reaction:
C₅H₁₂ (g)+ 8 O₂ (g) $\rightarrow$ 5 CO₂ (g) + 6 H₂O (g), using the following bond enthalpies given (in kJ mol^-1):
C-H = + 412
C=O = + 742
C-O = + 358
C-C = + 347
O=O = + 498
O-H = + 464

A) + 2325 kJ mol^-1.
B) - 2672 kJ mol^-1.
C) + 2672 kJ mol^-1
D) - 2325 kJ mol^-1.

Question 35

Calculate the enthalpy change for the following reaction :
C₂H₆O (g)+ 3 O₂ (g) $\rightarrow$ 2 CO₂ (g) + 3 H₂O (g), using the bond enthalpies given (in kJ mol^-1):
C-H = + 412
C=O = + 742
C-O = + 358
C-C = + 347
O=O = + 498
O-H = + 464

A) - 1081 kJ mol^-1.
B) + 1081 kJ mol^-1.
C) + 1029 kJ mol^-1.
D) - 1029 kJ mol^-1.

Question 36

The enthalpy change for the complete combustion of 1 mol of methane at 1 bar and 298 K is - 890.3 kJ mol^-1.
Calculate at 335 K.
Mean C_p / J K^-1 mol^-1: CH₄ (g) 35.7; O₂ (g) 29.4; CO₂ (g) 37.1; H₂O (l) 75.3.

A) - 890.3 kJ mol^-1.
B) - 859.1 kJ mol^-1.
C) - 888.8 kJ mol^-1.
D) - 886.9 kJ mol^-1.

Question 37

The enthalpy change for the complete combustion of 1 mol of hydrogen at 1 bar and 298 K is - 286 kJ mol^-1.
Calculate at 323 K (in kJ mol^-1).
Mean C_p / J K^-1 mol^-1: H₂ (g) 28.8; O₂ (g) 29.4; CO₂ (g) 37.1; H₂O (l) 75.3.

A) + 1304.
B) - 286.
C) - 284.
D) - 265.

Question 38

When 1 mole of gas expands from a volume of 2.5 dm³ to 5 dm³ against a constant pressure of 1 atm, which of the following are true? Select all that apply.

A) Work is done by the system.
B) Work is done on the system.
C) Energy is gained by the system.
D) Energy is lost by the system.

Question 39

A reaction produces hydrogen gas. A balloon attached to the reaction vessel expands against a constant pressure of 1 atm and at the end of the reaction it is calculated that 1.5 dm³ of H₂ (g) has been produced. Calculate the energy transferred as work, w, (in J).

A) - 152.
B) + 152.
C) - 1.5.
D) - 1.5 × 10^-3.

Question 40

When 1 mol of gas expands from a volume of 2.5 dm³ to 5 dm³ against a constant pressure of 1 atm, calculate the energy transferred as work, w, (in J).

A) - 2.5 × 10^-3.
B) + 253.
C) - 253.
D) - 2.5.

Question 41

The First Law of thermodynamics states the principle of conservation of energy that the total quantity of energy in the Universe is ________.

Question 42

One mole of gas is heated with 1.75 kJ of energy; it expands doing 250 J of work. Calculate the change in internal energy of the gas.

A) + 1500 J.
B) + 2000 J.
C) - 1500 J.
D) - 2000 J.

Question 43

For a reaction conducted at constant pressure and at 298 K the change in number of moles of gas (Δn_gas) is + 2. Calculate the difference (in kJ mol^-1) between ΔH (enthalpy change) and ΔU (internal energy).

A) - 4.96
B) + 4.96.
C) + 2.
D) - 2.

Question 44

For a reaction conducted at constant pressure and at 298 K the change in number of moles of gas (Δn_gas) is - 1. Calculate the difference (in kJ mol^-1) between ΔH (enthalpy change) and ΔU (internal energy).

A) + 2.48.
B) - 2.48.
C) + 1.
D) - 1.

Question 45

The combustion of ethanol (C₂H₅OH) at 1 bar and 298 K releases 1367 kJ mol^-1 of heat.
C₂H₅OH (l) + 3 O₂ (g) $\rightarrow$ 2 CO₂ (g) + 3 H₂O (l) Calculate $\Delta_{c} U_{208}^{\prime}$ (in kJ mol^-1) for ethanol.

A) + 1110.
B) - 3845.
C) - 1369.
D) -1365.

Question 46

Which of the following correctly characterise a bomb calorimeter? Select all that apply.

A) It measures the internal energy change of a reaction.
B) It measures the enthalpy change of a reaction.
C) It is a reaction chamber where the temperature is kept constant.
D) It can measure many different reactions.

Question 47

The calibration factor of a bomb calorimeter was calculated to be 10.27 kJ K^-1. Calculate the internal energy change of combustion for glucose (M_r = 180.16) if the combustion at 298 K of 1.228 g caused a temperature rise of 1.847 K.

A) - 2783.
B) + 19.
C) - 19.
D) + 2783.