Em tham khảo nha:
\(\begin{array}{l}
a)\\
\% {m_N}\,trong\,CO{(N{H_2})_2} = \dfrac{{14 \times 2}}{{60}} \times 100\% = 46,67\% \\
\% {m_{N\,}}trong\,{(N{H_4})_2}S{O_4} = \dfrac{{14 \times 2}}{{132}} \times 100\% = 21,21\% \\
\% {m_N}\,trong\,N{H_4}N{O_3} = \dfrac{{14 \times 2}}{{80}} \times 100\% = 35\% \\
\Rightarrow\text{ Nên chọn phân } {\rm{Ur}}e(CO{(N{H_2})_2})\\
b)\\
{m_N}\,trong\,CO{(N{H_2})_2} = 500 \times 46,67\% = 233,35g
\end{array}\)