In: Chemistry
Use standard heat of formations to find the heat for the combustion of 5.0 g of Methane gas CH4 to form carbon dioxide and water vapor
BALANCED EQUATION : CH4(g) + 2O2(g) ---> CO2(g) +
2H2O(l)
DH0rxn = (1*DH0f,CO2 + 2*DH0f,H2O)-(1*DH0f,Ch4+2*DH0f,O2)
= (1*-393.5 + 2*-285.8)-(1*-74.81+2*0)
= -890.29 kj/mol
no of mol of CH4 burned = w/Mwt
= 5/16
= 0.3125 mol
1 mol CH4 = 815.48 kj
so that, heat released(q) = n*DHrxn
= 0.3125*890.3
= 278.22 kj
DHcomb = -278.22 kj