Quiz 1- Thermochemistry

Determine the amount of heat produced per kg of CO2 formed during the combustion of benzene.

2 C6H6(l) + 15 O2(g) → 12 CO2(g) + 6 H2O(g)  

                                                                      ΔH = − 6278 kJ

• –1.43 × 10⁵ kJ/kg

• –2.30 × 10⁴ kJ/kg

• –4.34 × 10⁴ kJ/kg

• –1.19 × 10⁴ kJ/kg

• –8.40 × 10⁵ kJ/kg

1. Which of the following reaction(s) is the enthalpy change for the reaction NOT equal to ΔH°f of the product?

1. I. 2 H(g) → H2(g)

2. II. H2(g) + O2(g) → H2O2(l)

3. III. H2O(l) + O(g) → H2O2(l)

• I only

• II Only

• III Only

• I and III Only

5. Which of the following statements is true?

• • Enthalpy is a path function.

• • The enthalpy change for a reaction is the reciprocal of the ΔH of the reverse reaction.

• • The enthalpy change for a reaction is independent of the states of the reactants and products.

• • Bromine exists as a gas in nature.

• • Enthalpy (H) is the value of heat (q) measured under conditions of constant pressure.

1. Use the following enthalpies to calculate ΔH°f for PbO(s).

PbO(s) + CO(g) → Pb(s) + CO2(g)      ΔH° = −131.4 kJ  

C(s, graphite) + O2(g) → CO2(g)          ΔH°f = −393.5 kJ/mol

C(s, graphite) + ½ O2(g) → CO(g)       ΔH°f = −110.5 kJ/mol

• •  −151.6 kJ/mol

• • −283.0 kJ/mol

• • +283.0 kJ/mol

• −372.6 kJ/mol

• • +252.1 kJ/mol

1. Consider the following reaction:

2 SO2(g) + O2(g) → 2 SO3(g)    ΔH° = −198 kJ

          The ΔH°f for SO2(g) is −297 kJ/mol. Calculate the  

          ΔH°f  for SO3(g).  

• •  −396 kJ/mol

• −248 kJ/mol

• • −578 kJ/mol

• • 792 kJ/mol

• • −495 kJ/mol

1. Consider the following combustion reaction: CH4(g) + 2 O2(g)  → CO2(g) + 2 H2O(g)

2. Use average bond energies to predict the ΔH.  

• 6098kj/mole

• 824kj/mole

• -824kj/mole

• 6098kj/mole