Question

If 38.55 kJ of heat is absorbed when 6.0 g of O\(_2\) react with ClF according to the reaction: \[ \text{2ClF(g)} + \text{O}_2(g) \rightarrow \text{Cl}_2\text{O}(g) + \text{OF}_2(g) \] What is the standard enthalpy of reaction?

• A. 72.28 kJ
• B. 205.6 kJ
• C. 102.8 kJ
• D. 49.80 kJ

Hint:

When calculating standard enthalpy, always convert mass to moles using the molar mass, and then divide the total heat by moles to find the enthalpy per mole.

Answer 1

The Correct Option is B

Step 1: Calculate the number of moles of O\(_2\).
The molar mass of O\(_2\) is 32 g/mol. Therefore, the number of moles of O\(_2\) is: \[ \frac{6.0 \, \text{g}}{32 \, \text{g/mol}} = 0.1875 \, \text{mol} \]
Step 2: Calculate the heat absorbed per mole.
The total heat absorbed is 38.55 kJ. To find the heat absorbed per mole: \[ \text{Heat absorbed per mole} = \frac{38.55 \, \text{kJ}}{0.1875 \, \text{mol}} = 205.6 \, \text{kJ/mol} \]
Step 3: Conclusion.
The standard enthalpy of reaction is 205.6 kJ.