What mass of natural gas (ch4) must you burn to emit 272 kj of heat?

CH4 + 2 O2 ---> CO2 + 2 H2O Q = 891,6 kJ / mol CH4

1 mol CH4 = 16 g

16 g 891,6 kJ
x g 272 kJ

x = 272 kJ × 16 g / 891,6 kJ = 4,88 g

You must burn 4,88 g of CH4.

:-) ;-)

The answer is probably c. xylem