\[\begin{array}{l}
3Cu + 2NO_3^ - + 8{H^ + } \to 3C{u^{2 + }} + 2NO + {H_2}O\\
0,04....0,03....0,08\\
\to {H^ + }\,het\\
\\
dung\,\,dich\,sau\,phan\,ung\,gom\,\\
{n_{Cu}} = 0,01;{n_{C{u^{2 + }}}} = 0,03;{n_{N{a^ + }}} = 0,03;{n_{NO_3^ - }} = 0,01;{n_{SO_4^{2 - }}} = 0,04\\
\to {m_{muoi}} = {m_{C{u^{2 + }}}} + {m_{N{a^ + }}} + {m_{NO_3^ - }} + {m_{SO_4^{2 - }}} = 7,07
\end{array}\]