Question

Carbon reacts with oxygen to produce carbon dioxide which is an exothermic reaction, where $394kJ/mol$ of heat is produced. What will be the value of $\Delta H$ when $24$ grams of carbon reacts?

• A. $+394kJ$
• B. $-394kJ$
• C. $+788kJ$
• D. $-788kJ$

Answer 1

The correct option is D $-788kJ$

$C$ $+$ $O_2$ $=$ $C{O}_2$ $+$ $Heat$.

Thus, we see that $1$ mole or $12$ grams of carbon gives out $394kJ$ of heat.

$1g$ of carbon gives out $\frac{394}{12}$ $kJ$ of heat.

$24g$ of carbon will give out $\frac{394}{12}$$\times$$24$, that is $788kJ$ of heat.

Since the reaction is exothermic in nature, that is heat will be given out or produced.

Hence, the value of $\Delta H$ will be negative. Thus, $\Delta H$ is $-788kJ$.