Analía Bellizzi – Chemistry Classes

Ronald Reagan High School

Thermochemistry Exercise #1

AS Thermochemistry Exercise #1 Profile Diagrams

1. Draw enthalpy level diagrams for:

a.  an exothermic reaction
b.  an endothermic reaction

2. Indicate the values (positive or negative) for temperature and enthalpy changes in:

a.  an exothermic reaction

    • change in temperature sign:
    • enthalpy change sign:

b.  an endothermic reaction

    • change in temperature sign:
    • enthalpy change sign:

3. Indicate whether the following reactions are exothermic or endothermic.

a. Boiling Water
b. Freezing water
c. melting ice
d. condensing steam
e. burning wood
f. burning magnesium in air

4. Draw the enthalpy profile diagram for the following reactions.

a. CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)            ΔH = –890 kJ mol–1.  AE = 2000 kJ

b. H2(g) + I2(g) → 2HI(g)                                       ΔH = +53 kJ mol–1   AE = 184 kJ

5. Calculate the energy released when 4.8 g of methane, CH4, completely burns in oxygen.      Give your answer in kJ. Use the equation below [Mr: C = 12; H = 1]

CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) ΔH = –890 kJ mol–1