$C_6H_6\xrightarrow{{HNO_3, H_2SO_4}} C_6H_5NO_2$
Tỉ lệ khối lượng: $78kg$ benzen tạo $123kg$ nitrobenzen
$H=78\%$
a,
$m_{C_6H_6}=100kg$
$\to m_{C_6H_5NO_2}=\dfrac{100.123}{78}.78\%=123kg$
b,
$m_{C_6H_5NO_2}=100kg$
$\to m_{C_6H_6}=\dfrac{100.78}{123}:78\%=81,3kg$