Question

For which one of the following equation is $\Delta H_{react}^o$ equal to $\Delta H_f^o$ for the product?

• A. $N_2\left(g\right)+O_3\left(g\right)\to N_2{O}_3\left(g\right)$
• B. $C{H}_4\left(g\right)+2{Cl}_2\left(g\right)\to N_2{O}_3\left(g\right)$
• C. $Xe\left(g\right)+{2F}_2\left(g\right)\to {XeF}_4\left(g\right)$
• D. $2CO\left(g\right)+O_2\left(g\right)\to {2CO}_2\left(g\right)$

Answer 1

Answer: (D)

$2CO\left(g\right)+O_2\left(g\right)\to {2CO}_2\left(g\right)$

The heat of formation is defined as the heat generated or observed when the compound is formed from its component elements in their standard state.

By the definition (D) and (B) are incorrect as the starting material are compound.

(A) is incorrect as ozone is not the standard state for carbon.

Now (D) is correct as it satisfies the definition of heat of formation.