\(\%m_{Ca}=\dfrac{40}{164}.100=24,39\left(\%\right)\\ \%m_N=\dfrac{28}{164}.100=17,07\left(\%\right)\\ \%m_O=\dfrac{48.2}{164}.100=58,54\left(\%\right)\)

$M_{Ca(NO_3)_2} = 164$

$\%Ca = \dfrac{40}{164}.100\% = 24,39\%$
$\%N = \dfrac{14.2}{164}.100\% = 17,07\%$

$\%O = 100% -24,39\% -17,07\% = 58,54%%

+) Trong H₂SO₄ có: \(\left\{{}\begin{matrix}\%m_H=\dfrac{2}{98}\cdot100\%\approx2,04\%\\\%m_S=\dfrac{32}{98}\cdot100\%\approx32,65\%\\\%m_O=65,31\%\end{matrix}\right.\)

+) Trong HNO₃ có: \(\left\{{}\begin{matrix}\%m_H=\dfrac{1}{63}\cdot100\%\approx1,59\%\\\%m_N=\dfrac{14}{63}\cdot100\%\approx22,22\%\\\%m_O=76,19\%\end{matrix}\right.\)

a)Ta có:\(m\%_H=\dfrac{2.100\%}{98}=2,04\%\)

        \(m\%_S=\dfrac{32.100\%}{98}=32,65\%\)

        \(m\%_O=100-2,04-32,65=65,31\%\)

b) tương tự

\(M_{\left(NH_4\right)_2SO_4}=\left(14+1.4\right).2+32+16.4=132\left(\dfrac{g}{mol}\right)\)

\(\%N=\dfrac{14.2}{132}.100\%=21,2\%\)

\(\%H=\dfrac{1.4.2}{132}.100\%=6\%\)

\(\%S=\dfrac{32}{132}.100\%=24,2\%\)

\(\%O=\dfrac{16.4}{132}.100\%=48,5\%\)

$M_{hợp\ chất} = 98 + 63 = 161(đvC)$
$\%H = \dfrac{2 + 1}{161}.100\% = 1,86\%$
$\%S = \dfrac{32}{161}.100\% = 19,88\%$

$\%N = \dfrac{14}{161}.100\% = 8,7\%$
$\%O = \dfrac{16.4 + 16.3}{161}.100\% = 69,56\%$

Dễ ợt

\(a.\%m_N=\dfrac{14.2}{\left(14+4.1\right).2+32+4.16}.100\approx21,212\%\\ \%m_H=\dfrac{4.2}{\left(14+4.1\right).2+32+4.16}.100\approx6,061\%\\ \%m_S=\dfrac{32}{\left(14+4.1\right).2+32+4.16}.100\approx24,242\%\\ \%m_O=\dfrac{4.16}{\left(14+4.1\right).2+32+4.16}.100\approx48,485\%\)

\(b.m_{N\left(20kg\right)}=20.\dfrac{2.14}{\left(14+4.1\right).2+32+4.16}.100\%\approx4,2424\left(kg\right)\)