Heat capacity of water is 18 cal-degree-1-mol-1. The quantity of heat needed to rise temperature of 18g water by 0.2oC is X cal. Then amount of CH4(g) to be burnt to produce X cal heat is
(CH4+2O2 →CO2+2H2O, ΔH= –200K.Cal)
q =m CpΔT
= 3.6 cal
16gm -------200Kcal
? -------3.6 x 10-3 Kcal
= 288 x 10-6gm
= 0.288 mg