N%=2N / [(NH4)2SO4] X100%.....=(2X14) / [ (14+4X1)X2 + (32 + 16 X4)] X100% = 21.2%
N元素质量分数=N原子数目/硫酸铵相对分子质量×100%=14×2/(14×2+32+4×16）×100%=22.58%
