Question

The heat combustion of Butane ∆Ho
RXN is equal to the heat generated by the cooling of
17.2 g of water from 100Co
to 20Co (the specific heat for water is s = 4.186 J/g.C).
Calculate the mass of Butane that needs to be combusted to obtain 350 kJ of heat.

Answer 1

given,
delta H0 = heat generated by the cooling of 17.2 g of water from 100Co to 20Co  
= m*s*(T2 - T1)
= 17.2*4.186*(100 - 20)
= 5759.9 J
= 5.78 kJ

5.78 KJ of heat is produced by 1 mol of butane
1 KJ of heat is produced by 1/5.78 mol of butane
350 KJ of heat is produced by (1/5.78)*350 mol of butane
350 KJ of heat is produced by 60.56 mol of butane
so,
number of mole of Butane required = 60.56 mol
molar mass of butane = 58.1 g/mol
mass of Butane required = (number of mole of Butane required)*(molar mass of butane)
= 60.56*58.1
= 3518.5 g

Answer : 3518.5 g