A chemical compound has a molecular weight of 89.05 g/mole. 1.400 grams of this compound underwent complete combustion under constant pressure conditions in a special calorimeter. This calorimeter had a heat capacity of 2980 J Â°C.1 (Note that the calorimeter was made of a metal shell, a water "substitute" - a special oil, and a thermocouple). The temperature went up by 11.95 degrees.

Required:
Calculate the molar heat of combustion of the compound.

In this case, for such calorimetry problem, we can notice that the combustion of the compound releases the heat which causes the increase of the temperature by 11.95 °C, it means that we can write:

[tex]Q _{comb}=-C_{calorimeter}\Delta T_{calorimeter}[/tex]

In such a way, we can compute the total released heat due to the combustion considering the calorimeter specific heat and the temperature raise:

[tex]Q _{comb}=-2980\frac{J}{\°C} *11.95\°C\\\\Q _{comb}=-35,611J[/tex]

Next, we compute the molar heat of combustion of the compound by dividing by the moles, considering 1.400 g were combusted:

[tex]n=1.400g*\frac{1mol}{89.05g} =0.01572mol[/tex]

Thus, we obtain:

[tex]\Delta _{comb}H=\frac{Q_{comb}}{n}=\frac{-35,611J}{0.01572mol} \\\\\Delta _{comb}H=-2,265,331\frac{J}{mol}*\frac{1kJ}{1000J} \\\\\Delta _{comb}H=-2,265\frac{kJ}{mol}[/tex]

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