Enthalpy Stoichiometry Worksheet

Enthalpy Stoichiometry

Read each question carefully and provide clear, concise answers. Show all your work for calculations.

1. Which of the following statements correctly describes an exothermic reaction?

2. In an endothermic reaction, the system   energy from its surroundings.

3. Hess's Law states that the total enthalpy change for a reaction is independent of the   taken.

4. Consider the combustion of propane: C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(l) ΔH = -2220 kJ/mol. Calculate the heat released when 5.0 moles of propane are completely burned.

5. If 25.0 grams of water are formed in the reaction above, how much heat was released? (Molar mass of H₂O = 18.02 g/mol)

6. The standard enthalpy of formation for an element in its standard state is always zero.

7. Given the following reactions:

C(s) + O₂(g) → CO₂(g) ΔH₁ = -393.5 kJ

H₂(g) + ½O₂(g) → H₂O(l) ΔH₂ = -285.8 kJ

2C(s) + H₂(g) → C₂H₂(g) ΔH₃ = +226.7 kJ

Calculate ΔH for the reaction: C₂H₂(g) + ⁵/₂O₂(g) → 2CO₂(g) + H₂O(l)