Salt was obtained from ammonia with a mass of 5.1 g and nitrate acid with a mass of 12.6 g and dissolved in 200 g

Salt was obtained from ammonia with a mass of 5.1 g and nitrate acid with a mass of 12.6 g and dissolved in 200 g of water. What is the mass fraction of salt in the resulting solution?

NH3 + HNO3 = NH4NO3
n (NH3) = m / M = 5.1 / 17 = 0.3 mol
n (HNO3) = 12.6 / 63 = 0.2 mol
HNO3 is in short supply, so it counts
0.2 / 1 = x / 1
х = n (NH4NO3) = 0.2 mol
m (NH4NO3) = n * M = 0.2 * 80 = 16g
W (NH2NO3) = m (NH4NO3) / m (H2O) + m (NH4NO3) = 16g / 200 + 16 = 0.074 or 7.4%
answer: 7.4%