What mass of natural gas (CH4) must you burn to emit 264 kJ of heat?

CH4 (g) + 2O2 (g) →CO2 (g) + 2H2O (g) ΔH∘rxn=-802.3kJ

The heat released by cpmolete the combustion of organic products with oxygen is called heat of combustion.

Here 1 mol of CH4 realesed 802.3 KJ

To emit 264 kJ you multiply you need (1 mol of CH4/802.3 kJ) * 264 kJ = 0.329 mol of CH4

The molar mass, MM, of CH4 is 12 g/mol + 4*1g/mol = 16 g/mol

The to obtain the mass multiply the number of moles times the molar mass:

mass = n * MM = 0.329mol * 16g/mol = 5.26 grams

Answer: 5.26 grams