Gọi hoá trị của A là n
Gọi \(n_{Al}=n_A=a\left(mol\right)\)
\(n_{N_2O}=\dfrac{1,4}{22,4}=0,0625\left(mol\right)\)
PTHH: \(8Al+30HNO_3\rightarrow8Al\left(NO_3\right)_3+3N_2O+15H_2O\) (1)
\(8A+10nHNO_3\rightarrow8A\left(NO_3\right)_n+nN_2O+5nH_2O\) (2)
Theo PT: \(n_{NO_3\left(trong.muối\right)}=8n_{N_2O}=0,5\left(mol\right)\)
=> \(m_{kl}=40,2-0,5.62=9,2\left(g\right)\)
=> \(27a+aM_A=9,2\)
=> \(27+M_A=\dfrac{9,2}{a}\) (**)
BTe: \(3n_{Al}+n.n_A=8n_{N_2O}\)
=> \(3a+an=0,5\)
=> \(a=\dfrac{0,5}{n+3}\) (**)
Từ (*), (**)
=> \(27+M_A=\dfrac{9,2}{\dfrac{0,5}{n+3}}=18,4\left(n+3\right)=18,4n+55,2\)
=> \(M_A=18,4n+55,2-27=28,2+18,4n\left(g/mol\right)\)
Xét \(n=2\) thoả mãn => MA = 28,2 + 18,4.2 = 65 (g/mol)
=> A là Zn
