Enthalpy Stoichiometry Worksheet

Enthalpy Stoichiometry

Read each question carefully and provide detailed answers. Show all your work for calculation problems.

1. Which of the following best describes an exothermic reaction?

2. What is the standard enthalpy of formation (ΔH°f) for an element in its most stable form?

3. The heat absorbed or released in a chemical reaction at constant pressure is called the  .

4. Hess's Law states that if a reaction can be expressed as the sum of two or more steps, the enthalpy change for the overall reaction is the   of the enthalpy changes for the individual steps.

5. Consider the following reaction: 2H₂(g) + O₂(g) → 2H₂O(l) ΔH = -571.6 kJ. Is this reaction endothermic or exothermic? Justify your answer.

6. Calculate the enthalpy change (ΔH) for the following reaction using the given standard enthalpies of formation (ΔH°f): C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(l) Given: ΔH°f [C₃H₈(g)] = -103.8 kJ/mol ΔH°f [CO₂(g)] = -393.5 kJ/mol ΔH°f [H₂O(l)] = -285.8 kJ/mol ΔH°f [O₂(g)] = 0 kJ/mol

7. Energy is neither created nor destroyed in a chemical reaction.

8. A positive enthalpy change (ΔH) indicates an exothermic reaction.

Match the term with its definition.