Question

Given: 2C(s) + O₂(g) \(\rightarrow\) 2CO₂(g); \[ \Delta H = -787 \, \text{kJ} \] H₂(g) + \( \frac{1}{2} \)O₂(g) \(\rightarrow\) H₂O(l); \[ \Delta H = -286 \, \text{kJ} \] C₂H₂(g) + \( \frac{5}{2} \)O₂(g) \(\rightarrow\) 2CO₂(g) + H₂O(l); \[ \Delta H = -1310 \, \text{kJ} \] The heat of formation of acetylene is

• A. \( -1802 \, \text{kJ} \)
• B. \( +1802 \, \text{kJ} \)
• C. \( +237 \, \text{kJ} \)
• D. \( -800 \, \text{kJ} \)

Hint:

Use Hess’s law to add enthalpy changes of individual reactions to calculate the total enthalpy change.

Answer 1

The Correct Option is A

Step 1: Using Hess’s Law.
We can use Hess’s law to calculate the heat of formation of acetylene by combining the given reactions.

Step 2: Conclusion.
Thus, the heat of formation of acetylene is \( -1802 \, \text{kJ} \). The correct answer is option (A).

Final Answer: \[ \boxed{\text{(A) } -1802 \, \text{kJ}} \]