Question

One gram sample of ${NH}_4{NO}_3$ is decomposed in a bomb calorimeter. The temperature of the calorimeter increase by $6.12K$. The heat capacity of the system is $1.23kJ/g/K.$ What is the molar heat of decomposition for ${NH}_4{NO}_3$?

• A. $7.53kJ/mol$
• B. $398.1kJ/mol$
• C. $16.1kJ/mol$
• D. $602kJ/mol$

Answer 1

Answer: (D)

$602kJ/mol$

Heat = mass $\times$ specific heat $\times$ temp change

Heat = $1$ g $\times$ $1.23$ $\times$ $6.12$

$=7.527kJ$

So since molar mass of the sample is $80g/mol$, the sample of one gram

$=1/80$ moles.

Since $1/80$ moles released $7.52kJ$, $1$ mole will release $80$ $\times$ $7.527kJ$

$=602.2kJ/mol$

So the correct answer is D