Mr(C6H6) = 12*6 + 1*6 = 78
Mr(H2SO3) = 1*2 + 32 + 16*3 = 82
Mr(H2CO3) = 1*2 + 12 + 16*3 = 62
Mr(P2O5) = 31*2 + 16*5 = 142
Mr(N2O3) = 14*2 + 16*3 = 76
Mr(HF) = 1 + 19 = 20
Mr(C6H6) = 12*6 + 1*6 = 78
Mr(H2SO3) = 1*2 + 32 + 16*3 = 82
Mr(H2CO3) = 1*2 + 12 + 16*3 = 62
Mr(P2O5) = 31*2 + 16*5 = 142
Mr(N2O3) = 14*2 + 16*3 = 76
Mr(HF) = 1 + 19 = 20