2Al+3Cu(NO3)2=3Cu+2Al(NO3)3
A Al=27g/mol
A Cu=64g/mol
M Cu(NO3)2=ACu+2AN+6AO=188g/mol
2*27gAl.......3*188g Cu(NO3)2.....3*64g Cu
400g Al......x.....y
x=400*3*188/54=4177,777g Cu(NO3)2
y=400*3*64/54=1422,222g Cu
n Cu(NO3)2=4177,777/188=22,222moli
n Cu=1422,222/64=22,222moli