CH4 Energy and Chemical Reactions

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Question #1

Coal is a common fuel used for heating and cooking in many parts of the world. Calculate the fuel value of coal (assume that coal is pure graphite).

A 65.53 kJ/g

B 4.726 x 103 kJ/g

C -393.5 kJ/mol

D 32.76 kJ/g

Question #2

A cheese pizza contains 10.2 g fat/100 g. Calculate the percentage of BMR (= 1750 Cal/day) available from the fat in a 400-g cheese pizza.

A 5.2 %

B 41 %

C 21 %

D 0.58 %

Question #3

Calculate the heat of combustion of propane according to the equation below.
C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l)

A -2219.9 kJ/mol

B -103.8 kJ/mol

C -2427.5 kJ/mol

D -783.1 kJ/mol

Question #4

Choose the correct chemical equation related to the standard enthalpy of formation of (CH3)3N.

A 4 (CH3)3N(l) + 21 O2(g) → 12 CO2(g) + 18 H2O(l) + 2 N2(g)

B 6 C(s, graphite) + 9 O2(g) + H2(g) + N2(g) → 2 (CH3)3N(l)

C 2 (CH3)3N(l) → 12 C (s, graphite) + 6 H2(g) + N2(g)

D 3 C(s, graphite) + 9/2 H2(g) + 1/2 N2(g) → (CH3)3N(l)

Question #5

The standard enthalpy of formation of KCl(s) is -436.7 kJ/mol, and the standard enthalpy of formation of KCl(aq, 1m) is -419.5 kJ/mol. Determine the standard enthalpy of solution of KCl.

A +856.2 kJ/mol

B +17.2 kJ/mol

C -402.3 kJ/mol

D -17.2 kJ/mol

E +856.2 kJ/mol

Question #6

Copper is a good heat-transfer material. How much heat must be absorbed from 0.500 kg copper to change its temperature from 26.0 °C to -63.0 °C? The specific heat capacity (Cu) = 0.385 J/g °C.

A 1.30 J

B -186 J

C 17.1 J

D 1.71×104 J

Question #7

When a 6.49-g sample of CaCl2 dissolves in 250 g water in a coffee cup calorimeter, the temperature rises from 22.0 to 26.6 °C. Calculate the change in enthalpy for this solution-making process. Express your answer in kilojoules per mole of salt. (Assume the solution has a density of 1.00 g/mL and specific heat of 4.184 J/g°C.)

A 0.0434 kJ/mol

B -82.3 kJ/mol

C -534 kJ/mol

D 82.3 kJ/mol

Question #8

Choose the molecule that has the weakest chemical bond, based on this data:
Bond Bond Enthalpy (kJ/mol)
H–F 566
H–Cl 431
H–Br 366
H–I 299

A HCl

B HBr

C HF

D HI

Question #9

It takes about 41.84 J of energy to raise the temperature of 10.0 g water from 23.4 to 24.4 °C. If we place 10.0 g water at 23.0 °C into a refrigerator at 6.0 °C, calculate how many joules of energy are transferred from the water to the refrigerator

A 711 J

B 962 J

C 377 J

D 251 J

Question #10

What is the correct standard thermochemical expression for the formation of H2O by burning H2 and O2?

A H2O(l) → 2 H2(g) + O2(g) ΔH° = -285.8 kJ

B 2 H2(g) + O2(g) → 2 H2O(g) ΔH° = -285.8 kJ

C H2(g) + ½ O2(g) → H2O(l) ΔH° = -285.8 kJ

D H2(g) + ½ O2(g) → H2O(g) ΔH° = -285.8 kJ

Question #11

Define the term “enthalpy change.”

A Heat transfer at constant temperature

B Heat transfer at constant pressure

C Heat transfer at constant volume

D Heat transfer with volume and pressure varying

Question #12

Which one of these processes is exothermic?

A Photosynthesis

B Microwaving popcorn

C Freezing ice cubes

D melting butter

Question #13

An electric heater is used to supply 36.3 J of energy to a 21.0-g graphite block with an initial temperature of 20.3 °C. Determine the final temperature of the graphite. (Specific heat of graphite = 0.72 J/g °C.)

A 1079 °C

B 18 °C

C 2.4 °C

D 23 °C

Question #14

Choose the process that requires the most energy when the temperature of 23.4 g ice at -25.0 °C is raised to 37.0 °C.

A Melting the ice

B All of the processes require essentially the same amount of energy.

C Warming the water

D Warming the ice to 0.0 °C

Question #15

The total internal energy of the system depends on

A only the number of particles present.

B only the temperature.

C temperature, type of particles and number of particles present

D only the type of particles.

Question #16

Which equation states the law of conservation of energy?

A E = 1/2 mv2

B E = mc2

C ΔE = q + w

D w = PΔV

Question #17

If you leave a 30-g silver spoon that was initially at 40 °C in a 250 mL drink at 50 °C for five minutes, what is likely to happen?

A Nothing will happen.

B The drink will get cooler, but the spoon will remain at the same temperature.

C The spoon will get cooler.

D The spoon and the drink will have the same temperature.

Question #18

Convert 23.2 kJ to Cal.

A 5.5 Cal

B 5.5×103 Cal

C 9.7×104 Cal

D 97 Cal

Question #19

Which statement describes an example of change in potential energy?

A Ions moving through a solution toward an oppositely charge electrode

B Molecules moving through a liquid

C Slowing a car by depressing the brakes

D A candy bar is metabolized by your body

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CH4 Energy and Chemical Reactions

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