Question

When 0.627 g of biphenyl (CH) combusts in a bomb calorimeter, the temperature rises from 21.9 C to 26.6 C. What is U for the reaction in kJ/mol biphenyl

Answer 1

Answer:

$U=-6852\frac{kJ}{mol}$

Explanation:

Hello there!

In this case, since the heat capacity of the bomb calorimeter, we can use this found value on ethernet: 5.86 kJ/°C, thus, we can compute the heat gained by the calorimeter:

$Q_{calorimeter}=C\Delta T=5.86kJ/\°C*(26.6-21.9)\°C=27.54kJ$

Thus, since the heat gained by the calorimeter is actually the heat released due to the combustion of byphenyl, we compute it as the negative of that of the calorimeter:

$Q_{combustion}=-Q_{calorimeter}=-27.54kJ$

Finally the energy of reaction, U, in kJ/mol for the combustion of byphenyl (molar mass = 154 g/mol) is:

$U=\frac{-27.54kJ}{0.627g*\frac{1mol}{156g} } \\\\U=-6852\frac{kJ}{mol}$

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