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Question

A quantity of 1.6 g sample of NH4NO3 is decomposed in a bomb calorimeter. The temperature of the calorimeter decreases by 6.0 K. The heat capacity of the calorimeter system is 1.25 kJ/K. The molar heat of decomposition for NH4NO3 is

Options

A.7.5 kJ/mol
B.−600 kJ/mol
C.−375 kJ/mol
D.375 kJ/mol

Solution

As the temperature is decreased, the reaction must be endothermic.

Heat absorbed in reaction = Heat released by calorimeter

$= c.\Delta T = 1.25 \times 6 = 7.5\text{ kJ} $$$\therefore\Delta H = + \frac{7.5}{1.6} \times 80 = + 375\text{ kJ/mol}$$

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