Deck 6: Thermochemistry

Question 1

Which of the following is TRUE if U = -95 J?

A) The system is gaining 95 J, while the surroundings are losing 95 J.
B) The system is losing 95 J, while the surroundings are gaining 95 J.
C) Both the system and the surroundings are gaining 95 J.
D) Both the system and the surroundings are losing 95 J.
E) None of the above are true.

Answer 1

The system is losing 95 J, while the surroundings are gaining 95 J.

Question 2

Which of the following statements is FALSE?

A) The internal energy of a system is the sum of all of its kinetic and potential energy.
B) Internal energy is a state function.
C) A chemical system exchanges energy with its surroundings through heat or work.
D) The total change in internal energy is the sum of heat transferred and work done.
E) Energy entering the system through heat or work carries a negative sign.

Answer 2

Energy entering the system through heat or work carries a negative sign.

Question 3

Energy that is associated with the position or composition of an object is called

A) kinetic energy.
B) thermal energy.
C) potential energy.
D) chemical energy.

Answer 3

potential energy.

Question 4

A piece of iron (C = 0.449 J g^-1 °C^-1 and a piece of gold (C = 0.128 J g^-1 °C^-1) have identical masses. If the iron has an initial temperature of 498 K and the gold has an initial temperature of 298 K, which of the following statements is TRUE of the outcome when the two metals are placed in contact with one another? Assume no heat is lost to the surroundings.

A) Since the two metals have the same mass, the final temperature of the two metals will be 398 K, exactly halfway between the two initial temperatures.
B) Since the two metals have the same mass, but the specific heat capacity of gold is much smaller than that of iron, the final temperature of the two metals will be closer to 298 K than to 498 K.
C) Since the two metals have the same mass, the thermal energy contained in the iron and gold after reaching thermal equilibrium will be the same.
D) Since the two metals have the same mass, the thermal energy contained in each metal after equilibrium will be the same.
E) None of the above is true.

Question 5

Define heat capacity.

A) the quantity of heat required to raise the temperature of 1 mol of a substance by 1 °C
B) the quantity of heat required to change a system's temperature by 1 °C
C) the quantity of heat required to raise the temperature of 1 g of a substance by 1 °C
D) the quantity of heat required to raise the temperature of 1 g of a substance by 1 °F
E) the quantity of heat required to raise the temperature of 1 L of a substance by 1 °C

Question 6

Identify the unit of specific heat capacity.

A) °C^-1
B) J g^-1 °C^-1
C) J mol^-1 °C^-1
D) g °C^-1
E) mol °C^-1

Question 7

Define specific heat capacity.

A) the quantity of heat required to raise the temperature of 1 mol of a substance by 1 °C
B) the quantity of heat required to change a system's temperature by 1 °C
C) the quantity of heat required to raise the temperature of 1 g of a substance by 1 °C
D) the quantity of heat required to raise the temperature of 1 g of a substance by 1 °F
E) the quantity of heat required to raise the temperature of 1 L of a substance by 1 °C

Question 8

Determine the specific heat capacity of an alloy that requires 59.3 kJ to raise the temperature of 150.0 g alloy from 298 K to 398 K.

A) 4.38 J °C^-1
B) 2.29 J °C^-1
C) 3.95 J °C^-1
D) 2.53 J °C^-1
E) 1.87 J °C^-1

Question 9

Calculate the amount of heat (in kJ) necessary to raise the temperature of 47.8 g benzene by 57.0 K. The specific heat capacity of benzene is 1.05 J g^-1 °C^-1.

A) 1.61 kJ
B) 16.6 kJ
C) 2.59 kJ
D) 2.86 kJ
E) 3.85 kJ

Question 10

Which of the following substances (with specific heat capacity provided) would show the greatest temperature change upon absorbing 100.0 J of heat?

A) 10.0 g Ag, C_Ag = 0.235 J g^-1 °C^-1
B) 10.0 g H₂O, = 4.184 J g^-1 °C^-1
C) 10.0 g ethanol, C_ethanol = 2.42 J g^-1 °C^-1
D) 10.0 g Fe, C_Fe = 0.449 J g^-1 °C^-1
E) 10.0 g Au, C_Au = 0.128 J g^-1 °C^-1

Question 11

For U to always be -, what must be true?

A) q = w
B) +q > -w
C) +w > -q
D) -w > +q

Question 12

Calculate the amount of heat (in kJ) required to raise the temperature of a 79.0 g sample of ethanol from 298.0 K to 385.0 K. The specific heat capacity of ethanol is 2.42 J g^-1 °C^-1.

A) 57.0 kJ
B) 16.6 kJ
C) 73.6 kJ
D) 28.4 kJ
E) 12.9 kJ

Question 13

Define molar heat capacity.

A) the quantity of heat required to raise the temperature of 1 mol of a substance by 1 °C
B) the quantity of heat required to change a system's temperature by 1 °C
C) the quantity of heat required to raise the temperature of 1 g of a substance by 1 °C
D) the quantity of heat required to raise the temperature of 1 g of a substance by 1 °F
E) the quantity of heat required to raise the temperature of 1 L of a substance by 1 °C

Question 14

Which of the following signs on q and w represent a system that is doing work on the surroundings as well as losing heat to the surroundings?

A) q = - , w = -
B) q = +, w = +
C) q = -, w = +
D) q = +, w = -
E) None of these represent the system referenced above.

Question 15

Identify the unit of heat capacity.

A) J °C^-1
B) J g^-1 °C^-1
C) J mol^-1 °C^-1
D) g °C^-1
E) mol °C^-1

Question 16

A sample of copper absorbs 43.6 kJ of heat, resulting in a temperature rise of 75.0 °C. Determine the mass (in kg) of the copper sample if the specific heat capacity of copper is 0.385 J g^-1 °C^-1.

A) 1.51 kg
B) 6.62 kg
C) 1.26 kg
D) 7.94 kg
E) 3.64 kg

Question 17

Calculate the change in internal energy (ΔU) for a system that is giving off 45.0 kJ of heat and is performing 855 J of work on the surroundings.

A) 44.1 kJ
B) -44.1 kJ
C) -45.9 kJ
D) 9.00 × 10² kJ
E) -9.00 × 10² kJ

Question 18

Which of the following signs on q and w represent a system that is doing work on the surroundings as well as gaining heat from the surroundings?

A) q = +, w = -
B) q = -, w = +
C) q = +, w = +
D) q = -, w = -
E) None of these represent the system referenced above.

Question 19

The water at the top of a waterfall contains ________ energy.

A) kinetic
B) thermal
C) potential
D) gravitational
E) magnetic

Question 20

Which of the following (with specific heat capacity provided) would show the smallest temperature change upon gaining 200.0 J of heat?

A) 50.0 g Al, C_Al = 0.903 J g^-1 °C^-1
B) 50.0 g Cu, C_Cu = 0.385 J g^-1 °C^-1
C) 25.0 g granite, C_granite = 0.79 J g^-1 °C^-1
D) 25.0 g Au, C_Au = 0.128 J g^-1 °C^-1
E) 25.0 g Ag, C_Ag = 0.235 J g^-1 °C^-1

Question 21

Calculate the change in internal energy (ΔU) for a system that is absorbing 35.8 kJ of heat and is expanding from 8.00 to 24.0 L in volume at 1.00 bar. (Remember that 100 J = 1 L bar)

A) +51.8 kJ
B) -15.8 kJ
C) -16.6 kJ
D) -29.3 kJ
E) +34.2 kJ

Question 22

A 4.98 g sample of aniline (C₆H₅NH₂, molar mass = 93.13 g ) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ . If the temperature rose from 29.5 °C to 69.8 °C, determine the value of U for the combustion of aniline.

A) +7.81 × 10³ kJ mol^-1
B) -3.20 × 10³ kJ mol^-1
C) +1.71 × 10³ kJ mol^-1
D) -1.71 × 10³ kJ mol^-1
E) -7.81 × 10³ kJ mol^-1

Question 23

If a reaction is carried out at constant volume, then the change in internal energy of the chemical reaction is equal to the ________.

A) heat evolved
B) work done by the system on the surroundings
C) work done by the surroundings on the system
D) heat evolved plus the work done by the surroundings
E) heat capacity of the system

Question 24

________ is a piece of equipment designed to measurechange in internal energy for combustion reactions.

A) Coffee cup calorimeter
B) Bomb calorimeter
C) Thermal calorimeter
D) Power compensation calorimeter
E) Isothermal calorimeter

Question 25

Calculate the amount (mass) of acetic acid (C₂H₄O₂, molar mass = 60.052 g mol^-1) that causes a bomb calorimeter with a heat capacity of 8.43 kJ °C^-1 to have a temperature increase from 24.5 °C to 36.8 °C. The Δ_rU for the combustion of acetic acid is -874.2 kJ mol^-1.

A) 6.18 g
B) 7.12 g
C) 2.18 g
D) 9.66 g
E) 8.68 g

Question 26

Calculate the amount (mass) of acetaldehyde (C₂H₄O, molar mass = 44.0526 g mol^-1) that causes a bomb calorimeter with a heat capacity of 12.91 kJ °C^-1 to have a temperature increase from 27.8 °C to 41.7 °C. The Δ_rU for the combustion of acetaldehyde is -1166.9 kJ mol^-1.

A) 6.77 g
B) 8.67 g
C) 4.29 g
D) 7.30 g
E) 5.55 g

Question 27

Determine the final temperature of a gold nugget (mass = 376 g) that starts at 398 K and loses 4.85 kJ of heat to a snowbank when it is lost. The specific heat capacity of gold is 0.128 J g^-1 °C^-1.

A) 133 K
B) 398 K
C) 187 K
D) 297 K
E) 377 K

Question 28

A 2.38 g sample of phenol (C₆H₆O, molar mass = 94.11 g ) was combusted in a bomb calorimeter with a heat capacity of 6.65 kJ . If the temperature increased from 23.8 °C to 35.4 °C, determine U for the combustion of phenol.

A) -8.19 × 10³ kJ mol^-1
B) -5.81 × 10³ kJ mol^-1
C) 4.87 × 10³ kJ mol^-1
D) -3.05 × 10³ kJ mol^-1
E) 2.41 × 10³ kJ mol^-1

Question 29

A chemist wishes to calibrate a bomb calorimeter, so she combusts 5.58 g of 4-pentenoic acid, Δ_combustionU = -26.77 kJ g^-1, which causes a temperature change from 23.4 °C to 38.9 °C. What should the chemist report for the value of C_cal?

A) 6.10 kJ °C^-1
B) 17.5 kJ °C^-1
C) 28.7 kJ °C^-1
D) 9.64 kJ °C^-1
E) 7.61 kJ °C^-1

Question 30

Calculate the internal energy change, Δ_rU, for the combustion of 9.467 g of L-alanine (C₃H₇NO₂, molar mass = 89.094 g mol^-1) if the combustion inside a bomb calorimeter, C_cal = 7.83 kJ °C^-1, causes a temperature change from 24.7 °C to 46.1 °C.

A) -1.58 × 10³ kJ mol^-1
B) 6.14 × 10³ kJ mol^-1
C) -3.48 × 10³ kJ mol^-1
D) -8.60 × 10² kJ mol^-1
E) 3.84 × 10³ kJ mol^-1

Question 31

Calculate the internal energy change, Δ_rU, for the combustion of 29.3 g of vitamin C (C₆H₈O₆, molar mass = 176.124 g mol^-1) if the combustion inside a bomb calorimeter, C_cal = 8.31 kJ °C^-1, causes a temperature change from 21.5 °C to 68.3 °C.

A) -1.78 × 10³ kJ mol^-1
B) -2.34 × 10³ kJ mol^-1
C) -6.03 × 10³ kJ mol^-1
D) -9.19 × 10² kJ mol^-1
E) -1.67 × 10² kJ mol^-1

Question 32

A 21.8 g sample of ethanol (C₂H₅OH) is burned in a bomb calorimeter according to the following reaction. If the temperature rises from 25.0 °C to 62.3 °C, determine the heat capacity of the calorimeter. The molar mass of ethanol is 46.07 g . C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(g) U = -1235 kJ mol^-1

A) 4.99 kJ °C^-1
B) 5.65 kJ °C^-1
C) 63.7 kJ °C^-1
D) 33.1 kJ °C^-1
E) 15.7 kJ °C^-1

Question 33

A 6.55 g sample of aniline (C₆H₅NH₂, molar mass = 93.13 g ) was combusted in a bomb calorimeter. If the temperature rose by 32.9 °C, use the information below to determine the heat capacity of the calorimeter. 4C₆H₅NH₂(l) + 35O₂(g) → 24CO₂(g) + 14H₂O(g) + 4NO₂(g)
Δ_rU= -3.20 × 10³ kJ mol^-1

A) 97.3 kJ
B) 38.9 kJ
C) 5.94 kJ
D) 6.84 kJ
E) 12.8 kJ

Question 34

The change in enthalpy for any process occurring at constant pressure is equal to the ________.

A) change in internal energy
B) heat at constant pressure
C) work done by the system
D) work done by the surroundings
E) internal energy plus the work done by the system

Question 35

A chemist wishes to calibrate a bomb calorimeter, so he combusts 7.529 g of D-galactose, Δ_combustionU = -15.48 kJ g^-1, which causes a temperature change from 26.38 °C to 34.60 °C. What should the chemist report for the value of C_cal?

A) 24.34 kJ °C^-1
B) 8.009 kJ °C^-1
C) 14.18 kJ °C^-1
D) 16.67 kJ °C^-1
E) 9.170 kJ °C^-1

Question 36

A balloon is inflated from 0.0100 L to 0.500 L against an external pressure of 10.00 bar. How much work is done in joules? (100 J = 1 L bar)

A) -49.0J
B) 49.0 J
C) 0.490 J
D) -0.490 J
E) -490 J

Question 37

Calculate the change in internal energy (ΔU) for a system that is giving off 25.0 kJ of heat and is changing from 12.00 L to 6.00 L in volume at 1.50 bar. (Remember that 100 J = 1 L bar)

A) +25.9 kJ
B) -16.0 kJ
C) -25.9 kJ
D) -24.1 kJ
E) 937 kJ

Question 38

An 8.21 g sample of glycerol (C₃H₈O₃, molar mass = 92.0938 g ) was combusted in a bomb calorimeter with a heat capacity of 10.61 kJ . If the temperature increased from 22.1 °C to 36.0 °C, determine U for the combustion of glycerol.

A) -4.38 × 10³ kJ mol^-1
B) 3.65 × 10³ kJ mol^-1
C) 2.18 × 10³ kJ mol^-1
D) -2.18 × 10³ kJ mol^-1
E) -1.65 × 10³ kJ mol^-1

Question 39

Identify what a bomb calorimeter measures.

A) measures ΔH for aqueous solutions
B) measures ΔU for combustion reactions
C) measures ΔH for oxidation solutions
D) measures ΔT for hydrolysis solutions
E) measures ΔU for reduction reactions

Question 40

Calculate the internal energy change, Δ_rU, for the combustion of 6.9261 g of diethylene glycol (C₄H₁₀O₃, molar mass = 106.120 g mol^-1) if the combustion inside a bomb calorimeter, C_cal = 13.84 kJ °C^-1, causes a temperature change from 22.8 °C to 34.0 °C.

A) -4.39 × 10³ kJ mol^-1
B) -9.16 × 10² kJ mol^-1
C) -2.37 × 10³ kJ mol^-1
D) 4.39 × 10³ kJ mol^-1
E) 1.18 × 10³ kJ mol^-1

Question 41

Which of the following processes is exothermic?

A) the formation of dew in the morning
B) the melting of ice
C) the chemical reaction in a "cold pack" often used to treat injuries
D) the vaporization of water
E) None of the above is exothermic.

Question 42

According to the following reaction, how much energy is required to decompose 55.0 kg of Fe₃O₄? The molar mass of Fe₃O₄ is 231.55 g . Fe₃O₄(s) → 3Fe(s) + 2O₂(g) H° = +1118 kJ

A) 1.10 × 10⁶ kJ
B) 2.38 × 10² kJ
C) 2.66 × 10⁵ kJ
D) 1.12 × 10³ kJ
E) 3.44 × 10⁴ kJ

Question 43

How much energy is evolved during the reaction of 48.7 g of Al according to the reaction below? Assume that there is excess Fe₂O₃. Fe₂O₃(s) + 2Al(s) → Al₂O₃(s) + 2Fe(s) H° = -852 kJ

A) 415 kJ
B) 207 kJ
C) 241 kJ
D) 130 kJ
E) 769 kJ

Question 44

How much energy is required to decompose 765 g of PCl₃ according to the reaction below? The molar mass of PCl₃ is 137.32 g and may be useful. 4PCl₃(g) → P₄(s) + 6Cl₂(g) H° = +1207 kJ

A) 2.31 × 10³ kJ
B) 4.33 × 103 kJ
C) 6.72 × 10³ kJ
D) 1.68 × 10³ kJ
E) 5.95 × 10³ kJ

Question 45

Using the following thermochemical equation, determine the amount of heat produced per kg of CO₂ formed during the combustion of benzene (C₆H₆). 2C₆H₆(l) + 15O₂(g) → 12CO₂(g) + 6H₂O(g) H° = -6278 kJ

A) 1.43 × 10⁵ kJ (kg CO₂)^-1
B) 2.30 × 10⁴ kJ (kg CO₂)^-1
C) 4.34 × 10⁴ kJ (kg CO₂)^-1
D) 1.19 × 10⁴ kJ (kg CO₂)^-1
E) 8.40 × 10⁵ kJ (kg CO₂)^-1

Question 46

A 35.6 g sample of ethanol (C₂H₅OH) is burned in a bomb calorimeter according to the following reaction. If the temperature rose from 35.0 °C to 76.0°C and the heat capacity of the calorimeter is 23.3 kJ , what is the value of ΔU°? The molar mass of ethanol is 46.07 g . C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(g) ΔU° = ?

A) -1.24 × 10³ kJ mol^-1
B) +1.24 × 10³ kJ mol^-1
C) -8.09 × 10³ kJ mol^-1
D) -9.55 × 10³ kJ mol^-1
E) +9.55 × 10³ kJ mol^-1

Question 47

A 6.55 g sample of aniline (C₆H₅NH₂, molar mass = 93.13 g ) was combusted in a bomb calorimeter with a heat capacity of 14.25 kJ . If the initial temperature was 32.9 °C, use the information below to determine the value of the final temperature of the calorimeter. 4C₆H₅NH₂(l) + 35O₂(g) → 24CO₂(g) + 14H₂O(g) + 4NO₂(g)
ΔU° = -1.28 × 10⁴ kJ

A) 257 °C
B) 46.6 °C
C) 96.1 °C
D) 41.9 °C
E) 931 °C

Question 48

Which of the following statements is TRUE?

A) Enthalpy is a state function.
B) An endothermic reaction has a negative enthalpy.
C) An exothermic reaction has a positive enthalpy.
D) Enthalpy change is zero under constant pressure.
E) The magnitude of enthalpy change is always positive.

Question 49

Using the following equation for the combustion of octane, calculate the amount of moles of carbon dioxide formed from 100.0 g of octane. The molar mass of octane is 114.33 g . The molar mass of carbon dioxide is 44.0095 g . 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O H° = -11018 kJ

A) 18.18 moles
B) 6.997 moles
C) 14.00 moles
D) 8.000 moles
E) 10.93 moles

Question 50

Using the following thermochemical equation, determine the amount of heat produced from the combustion of 24.3 g benzene (C₆H₆). The molar mass of benzene is 78.11 g . 2C₆H₆(l) + 15O₂(g) → 12CO₂(g) + 6H₂O(g) H° = -6278 kJ

A) 3910 kJ C₆H₆
B) 1950 kJ C₆H₆
C) 977 kJ C₆H₆
D) 40.1 kJ C₆H₆
E) 0.302 kJ C₆H₆

Question 51

The temperature rises from 25.00 °C to 29.00 °C when 3.50 g of sucrose undergoes combustion in a bomb calorimeter. Calculate U for the combustion of sucrose in kJ sucrose. The heat capacity of the calorimeter is 4.90 kJ . The molar mass of sugar is 342.3 g .

A) -1.92 × 10³ kJ mol^-1
B) 1.92 × 10³ kJ mol^-1
C) -1.23 × 10³ kJ mol^-1
D) 2.35 × 10⁴ kJ mol^-1

Question 52

Using the following equation for the combustion of octane, calculate the amount of moles of oxygen that reacts with 100.0 g of octane. The molar mass of octane is 114.33 g . The molar mass of carbon dioxide is 44.0095 g . 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O H° = -11018 kJ

A) 18.18 moles
B) 6.997 moles
C) 14.00 moles
D) 8.000 moles
E) 10.93 moles

Question 53

Which of the following processes is endothermic?

A) the freezing of water
B) the combustion of propane
C) a hot cup of coffee (system) cools on a countertop
D) the chemical reaction in a "hot pack" often used to treat sore muscles
E) the vaporization of rubbing alcohol

Question 54

Given w = 0, an endothermic reaction has which of the following properties?

A) +ΔH and -ΔU
B) -ΔH and +ΔU
C) +ΔH and +ΔU
D) -ΔH and -ΔU

Question 55

How much energy is evolved during the formation of 98.7 g of Fe according to the reaction below? Fe₂O₃(s) + 2Al(s) → Al₂O₃(s) + 2Fe(s) H° = -852 kJ

A) 753 kJ
B) 1.51 × 10³ kJ
C) 4.20 × 10³ kJ
D) 482 kJ
E) 241 kJ

Question 56

Using the following equation for the combustion of octane, calculate the heat of reaction for 100.0 g of octane. The molar mass of octane is 114.33 g . 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O H° = -11018 kJ

A) 4.82 × 10³ kJ
B) 4.82 kJ
C) 9.64 × 10³ kJ
D) 1.26 × 10⁴ kJ

Question 57

According to the following reaction, how much energy is evolved during the reaction of 32.5 g B₂H₆ and 72.5 g Cl₂? The molar mass of B₂H₆ is 27.67 g . B₂H₆(g) + 6Cl₂(g) → 2BCl₃(g) + 6HCl(g) H° = -1396 kJ

A) 1640 kJ
B) 238 kJ
C) 1430 kJ
D) 3070 kJ
E) 429 kJ

Question 58

Which of the following processes is endothermic?

A) an atom emits a photon
B) the condensation of water
C) an atom absorbs a photon
D) the electron affinity of a fluorine atom
E) None of the above processes is endothermic.

Question 59

A 12.8 g sample of ethanol (C₂H₅OH) is burned in a bomb calorimeter with a heat capacity of 5.65 kJ . Using the information below, determine the final temperature of the calorimeter if the initial temperature is 25.0°C. The molar mass of ethanol is 46.07 g . C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(g) U = -1235 kJ

A) 53.4 °C
B) 28.1 °C
C) 111 °C
D) 85.7 °C
E) 74.2 °C

Question 60

A bomb calorimeter with a heat capacity of 13.9 kJ °C^-1 has an initial temperature of 21.9 °C. If 5.00 g of propanal (C₃H₆O, molar mass = 58.0791 g mol^-1, Δ_rU = -1822.7 kJ mol^-1 for combustion) is combusted, calculate the final temperature of the calorimeter.

A) 26.1 °C
B) 16.7 °C
C) 33.2 °C
D) 43.1 °C
E) 34.0 °C

Question 61

Which of the following statements is TRUE?

A) State functions do not depend on the path taken to arrive at a particular state.
B) U can be determined using constant volume calorimetry.
C) Energy is neither created nor destroyed, excluding nuclear reactions.
D) H can be determined using constant pressure calorimetry.
E) All of the above are true.

Question 62

Calculate the heat transfer, in J, when 5.00 g of chromium (specific heat capacity = 0.449 J g^-1 °C^-1) at 0.00 °C is placed in 50.0 mL of water. The final temperature of the water is 23.8 °C. The chromium is defined as the system in this scenario.

A) -53 J
B) 53 J
C) 82 J
D) -82 J
E) 93 J

Question 63

An unknown metal alloy, mass = 36.1 g, has a temperature change of 31.6 to 24.8 °C after a heat transfer of -103.0 J. Calculate the specific heat capacity of the alloy.

A) 0.500 J g^-1 °C^-1
B) 0.384 J g^-1 °C^-1
C) 0.579 J g^-1 °C^-1
D) 0.420 J g^-1 °C^-1
E) 1.85 J g^-1 °C^-1

Question 64

According to the following thermochemical equation, what mass of H₂O (in g) must form to produce 975 kJ of energy? SiO₂(s) + 4HF(g) → SiF₄(g) + 2H₂O(l) H° = -184 kJ

A) 68.0 g
B) 102 g
C) 54.1 g
D) 191 g
E) 95.5 g

Question 65

Calculate the initial temperature of 21.8 g of lithium (specific heat capacity = 3.582 J g^-1 °C^-1) that absorbs 1642 J of energy from the surroundings and has a final temperature of 31.08 °C.

A) 52.11 °C
B) 38.04 °C
C) 26.74 °C
D) 10.05 °C
E) 3.17 °C

Question 66

Calculate the final temperature of 82.1 g of molecular hydrogen (specific heat capacity = 14.304 J g^-1 °C^-1) initially at 5.48 °C that absorbs 57 kJ of energy from the surroundings.

A) 14 °C
B) 24 °C
C) 34 °C
D) 44 °C
E) 54 °C

Question 67

Astatine is an extremely rare element with an estimated 28 g total on Earth. How much energy would be required to heat Earth's entire supply of astatine by 10.0 °C assuming it has a specific heat capacity similar to iodine, 0.214 J g^-1 °C^-1?

A) 60 J
B) 24 J
C) 130 J
D) 14 J
E) 250 J

Question 68

Two aqueous solutions are both at room temperature and are then mixed in a coffee cup calorimeter. The reaction causes the temperature of the resulting solution to fall below room temperature. Which of the following statements is TRUE?

A) The products have a lower potential energy than the reactants.
B) This type of experiment will provide data to calculate U.
C) The reaction is exothermic.
D) Energy is leaving the system during the reaction.
E) None of the above statements is true.

Question 69

Calculate the initial temperature of 448 g of grapes (specific heat capacity = 1.76 J g^-1 °C^-1) that absorb 17472 J of heat while warming up to room temperature, 23.1 °C.

A) 3.15 °C
B) 0.941 °C
C) -13.5 °C
D) 8.49 °C
E) 5.23 °C

Question 70

Calculate the final temperature of 6.84 g of praseodymium (specific heat capacity = 0.193 J g^-1 °C^-1) initially at 26.8 °C that releases 11.3 J of energy into the surroundings.

A) 14.3°C
B) 18.2 °C
C) 21.6 °C
D) 23.8 °C
E) 8.17 °C

Question 71

Using the following equation for the combustion of octane, calculate the amount of grams of carbon dioxide formed from 100.0 g of octane. The molar mass of octane is 114.33 g mol^-1. The molar mass of carbon dioxide is 44.0095 g mol^-1. 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O H° = -11018 kJ

A) 800.1 g
B) 307.9 g
C) 260.1 g
D) 792.3 g

Question 72

Calculate the initial temperature of 648 g of cucumber (specific heat capacity = 1.88 J g^-1 °C^-1) that absorbs 19857 J of heat while warming up to room temperature, 24.8 °C.

A) 9.62 °C
B) 8.50 °C
C) 10.3 °C
D) 14.8 °C
E) 3.41 °C

Question 73

Calculate the heat transfer, in kJ, when 1.287 kg of chicken breast (specific heat capacity = 1.82 J g^-1 °C^-1) is removed from a freezer at -17.3 °C and allowed to warm up to 0.00 °C. You need not be concerned about melting of ice or any other phase changes.

A) -0.0405 kJ
B) 0.0405 kJ
C) -40.5 kJ
D) 40.5 kJ
E) 8.65 kJ

Question 74

Calculate the heat transfer (J) when 3.15 g of platinum (specific heat capacity = 0.133 J g^-1 °C^-1) at 86.1 °C cools to room temperature, 24.3 °C.

A) -26 J
B) 26 J
C) -60 J
D) 60 J
E) -17 J

Question 75

What volume of benzene (C₆H₆, d = 0.88 g mL^-1, molar mass = 78.11 g mol^-1) is required to produce 1.5 × 10³ kJ of heat according to the following reaction? 2C₆H₆(l) + 15O₂(g) → 12CO₂(g) + 6H₂O(g) H° = -6278 kJ

A) 75 mL
B) 37 mL
C) 21 mL
D) 19 mL
E) 42 mL

Question 76

Calculate the final temperature of 68.4 g of molecular hydrogen (specific heat capacity = 14.304 J g^-1 °C^-1) initially at 8.24 °C that releases 25.3 kJ of energy into the surroundings.

A) 34.1 °C
B) 17.6 °C
C) -34.1 °C
D) -17.6 °C
E) -8.70 °C

Question 77

An unknown metal alloy, mass = 26.3 g, has a temperature increase of 8.31 °C after a heat transfer of 94.0 J. Calculate the specific heat capacity of the alloy.

A) 0.813 J g^-1 °C^-1
B) 0.517 J g^-1 °C^-1
C) 0.349 J g^-1 °C^-1
D) 0.288 J g^-1 °C^-1
E) 0.430 J g^-1 °C^-1

Question 78

According to the following reaction, how much energy is evolved during the reaction of 2.50 L B₂H₆ and 5.65 L Cl₂ (both gases are initially at STP)? The molar mass of B₂H₆ is 27.67 g . B₂H₆(g) + 6Cl₂(g) → 2BCl₃(g) + 6HCl(g) H° = -1396 kJ

A) 57.8 kJ
B) 156 kJ
C) 215 kJ
D) 352 kJ
E) 508 kJ

Question 79

Identify what a coffee cup calorimeter measures.

A) measures ΔH for aqueous solutions
B) measures ΔU for combustion reactions
C) measures ΔH for oxidation solutions
D) measures ΔT for hydrolysis solutions
E) measures ΔU for reduction reactions

Question 80

According to the following thermochemical equation, what mass of HF (in g) must react to produce 345 kJ of energy? Assume excess SiO₂. SiO₂(s) + 4HF(g) → SiF₄(g) + 2H₂O(l) H° = -184 kJ

A) 42.7 g
B) 37.5 g
C) 150. g
D) 107 g
E) 173 g