Дано
m(Cu)=6.4 g
m(ppaHNO3)=126 g
W(HNO3)=20%
η=90%
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V(NO2)-?
m(HNO3)=126*20%/100%=25.2 g
M(Cu)=64 g/mol
n(Cu)=m/M=6.4 / 64=0.1 mol
M(HNO3)=63 g/mol
n(HNO3)=m/M=25.2 / 63=0.4 mol
n(Cu)6,4 X
Cu+4HNO3(p)-->Cu(NO3)2+2NO2+2H2O Vm=22.4 L/mol
64 2*22.4
X=6.4 * 44.8 / 64 = 4.48 L
V(NO2)=4.48*90% / 100%
V(NO2)=4.032 L
ответ 4.032 л