Question

How much heat is released when 24.8 g of ch4 is burned in excess oxygen gas?

Answer 1

The given question is incomplete. The complete question is:

How much heat is produced when 24.8 g of $CH_4$ is burned in excess oxygen gas

Given: $CH _4 +2O_2\rightarrow CO_2+2H_2O$  ΔH= −802 kJ.

Answer: 1243.1 kJ

Explanation:

Heat of combustion is the amount of heat released on complete combustion of 1 mole of substance.

Given :

Amount of heat released on combustion of  1 mole of methane = 802 kJ kJ/mol

According to avogadro's law, 1 mole of every substance occupies 22.4 L at NTP, weighs equal to the molecular mass and contains avogadro's number $6.023\times 10^{23}$ of particles.

1 mole of $CH_4$ weighs = 16 g  

Thus we can say:  

16 g of $CH_4$ on combustion releases heat = 802 kJ

Thus 24.8 g of $CH_4$ on combustion releases =$\frac{802}{16}\times 24.8=1243.1kJ$

Thus heat released when 24.8 g of methane is burned in excess oxygen gas is 1243.1 kJ