Question

The heat of reaction for:
$C_{10}{H}_8\left(s\right)+12O_2\left(g\right)\to 10C{O}_2\left(g\right)+4H_{2}O\left(l\right)$
at constant volume is $-1228.2kcal$ at ${25}^{\circ }C$. The heat of reaction at constant pressure and same temperature is:

• A. $-1228.28kcal$
• B. $-1229.39kcal$
• C. $-1232.90kcal$
• D. $-1242.68kcal$

Answer 1

Answer: (B)

$-1229.39kcal$

$△E=-1228.2Kcal=-1228.2\times {10}^{3}cal$

For, constant temperature and pressure,
$△H=△E+△nRT$
$=-1228.2\times {10}^3+(-2)\left(2\right)\left(298\right)$
$=-1229392cal$
$=-1229.392kcal$

Hence, option B is correct