Question

When a 1.00-g sample of methane gas was burned with excess oxygen in the calorimeter, the temperature increased by 7.3°C. When

Answer 1

Answer:

The energies of  combustion (per gram) for hydrogen and methane are as follows: Methane = 82.5 kJ/g;  Hydrogen = 162 kJ/g

Note: The question is incomplete. The complete question is given below:

To compare the energies of combustion of these fuels, the  following experiment was carried out using a bomb  calorimeter with a heat capacity of 11.3 kJ/℃.  When a 1.00-g sample of methane gas burned with

excess oxygen in the calorimeter, the temperature  increased by 7.3℃. When a 1.00 g sample of  hydrogen gas was burned with excess oxygen, the temperature increase was 14.3°C. Compare the energies of  combustion (per gram) for hydrogen and methane.

Explanation:

From the equation of the first law of thermodynamics, ΔU = Q + W

Since there is no expansion work in the bomb calorimeter,  ΔU = Q

But Q = CΔT

where C is heat capacity of the bomb calorimeter =  11.3
kJ/ºC; ΔT = temperature change

For combustion of methane gas:

Q per gram = (
11.3
kJ/ºC * 7.3°C)/1.0g

Q = 83 kJ/g

For combustion of hydrogen gas:

Q per gram = (
11.3
kJ/ºC * 14.3°C)/1.0g

Q = 162 kJ/g