a) \(M_{\left(NH_2\right)_2CO}=\left(14.1+1.2\right).2+12.1+16.1=60\left(g/mol\right)\)
b) \(\left\{{}\begin{matrix}\%N=\dfrac{14.2}{60}.100\%=46,67\%\\\%H=\dfrac{1.4}{60}.100\%=6,67\%\\\%C=\dfrac{12.1}{60}.100\%=20\%\\\%O=100\%-46,67\%-6,67\%-20\%=26,66\%\end{matrix}\right.\)
\(a,M_{\left(NH_2\right)_2CO}=M_N.2+2.2.M_H+M_C+M_O\\ =14.2+4.1+12+16=60\left(\dfrac{g}{mol}\right)\)
\(b,\%m_N=\dfrac{14.2}{60}.100\approx46,667\%\\ \%m_H=\dfrac{4.1}{60}.100\approx6,667\%\\ \%m_C=\dfrac{12}{60}.100=20\%\\ \%m_O=\dfrac{16}{60}.100\approx26,667\%\)