Question

12.2gm solid benzoic acid is combusted in bomb calorie meter t ${25}^0$C? Rose from ${25}^0$C to ${75}^0$C if heat capacity of calorie meter is ${50JC}^0$? Calculate the change in internal energy? Calculate the molar enthalpy of combustion at ${25}^{0}C$.

Answer 1

Change in internal energy = heat cap. $\times \Delta$ T

$=50\times 50$

$=2500J$

$=2.5kJ$

n of benzoic acid = $\frac{12.2}{122}=0.1mol$

$\therefore 0.1$ mol needs $2.5kJ$

$1$ mol needs $2.5\times 10$

$=25kJ$

$\therefore$ Molar enthalpy is $25kJ$