Chapter 10, Problem 7STP

Interpretation Introduction

Interpretation:The value of $\Delta H$ needs to be determined.

Concept introduction: From Hess’s law we know that the total value of $\Delta H$ is the summation of all the H values.

  $\Delta H=H_1+H_2+H_3\mathrm{.........}$

Answer to Problem 7STP

D is the correct option.

Explanation of Solution

Given, half reactions are.

  $\begin{array}{l}\text{C}\left(\text{s}\right)\text{+}{\text{O}}_{\text{2}}\text{(g)}\to {\text{CO}}_{\text{2}}\left(\text{g}\right)\text{ΔH=}-\text{393}\text{.7}\text{kJ}\\ \text{2}\text{CO}\left(\text{s}\right)\text{+}{\text{O}}_{\text{2}}\text{(g)}\to {\text{2CO}}_2\left(\text{g}\right)\text{ΔH=}-\text{566}\text{.6}\text{kJ}\\ \end{array}$

Now, we have to calculate the $\text{ΔH}$ value of the reaction,

  $\text{2C}\left(\text{s}\right)\text{+}{\text{O}}_{\text{2}}\text{(g)}\to \text{2CO}\left(\text{g}\right)$

  $\Delta H=2\left(-393.7\right)+566.6=-220.8\text{kJ}$

Conclusion

The value of $\Delta H$ for the reaction, $\text{2C}\left(\text{s}\right)\text{+}{\text{O}}_{\text{2}}\text{(g)}\to \text{2CO}\left(\text{g}\right)$ is -220.8 kJ

Therefore, A, B and C are incorrect options.