Question

How many grams of methane must you burn (CH4 + 2O₂ DH = -891 kJ/mole) to heat 2.2 kilograms of water (C = 4.18 J/g C) 46.0°

Answer 1

The heat required to heat 2.2 kg of water by 46.0^o equals:

$Q=cm\Delta{T}=4.18\frac{J}{g\cdot\degree{C}}\times2200g\times46.0\degree{C}=4.23\times10^5J=423kJ$

Burning one mole of methane releases 891 kJ. Therefore,

$n(CH_4)=423kJ\times\frac{1mol(CH_4)}{891kJ}=0.475mol$

$m(CH_4)=0.475mol\times16.04\frac{g}{mol}=7.6g$

Answer: 7.6 g