a. A cylinder of gas is assumed to contain `11.2 kg` of butane. If a normal family needs `20000kJ` of energy per day for cooking, how long will the cylinder last? Given that the heat of combustion of butane is `2658 kJ mol^(-1)`.
b. If the air supply of the burner is insufficient (i.e. you have a yellow instead of a blue flame), a portion of the gas escape without combustion. Assuming that `33%` of the gas is wasted due to this inefficiency, how long would the cylinder last?

Explanation

(A) `C_(4)H_(10)(g) + 13/2 O_(2)(g) to 4CO_(2)(g) + 5H_(2)O(g)`
58 gm butane `to` 2658 kJ energy
11200 gm butane `=2658/58 xx 11200` kJ energy
Number of days `=(2568)/58 xx 11200/20000 = 26` days
(B) Number of days `=26 xx 0.67 = 17` days