How many grams of nitric acid(HNO3) will be produced when 0.51 mol of dinitrogen pentoxide reacts with water to form nitric acid?

Answer 1

mol mass N2O5 = 2*14 + 5*16 = 108 g/mol
mol mass HNO3 = 1 + 14 + 3*16 = 63 g/mol

for every N2O5 molecule you get two HNO3 molecules to balance the N atoms
so
.51 mol N2O5 ---> 1.02 mol HNO3
1.02mol * 63 g/mol = 64.26 g