Bài 4:
a, $2NaOH+ Cl_2 \to NaCl+ NaClO+ H_2O$
b, $MnO_2+ 4HCl \to MnCl_2+ Cl_2+ 2H_2O$
Bài 5:
$n_{HCl}= 0,15.0,5= 0,075 mol$
$2HCl+ Na_2CO_3 \to 2NaCl+ CO_2+ H_2O$
=> $n_{Na_2CO_3}= 0,0375 mol$
$C_{M_{Na_2CO_3}}= a= \frac{0,0375}{0,2}= 0,1875M$
Bài 6:
Gọi a, b là mol Al, Zn
=> $27a+65b= 18,4$ (1)
$n_{H_2}= 0,5n_{HCl}= 0,5 mol$
Bảo toàn e: $3a+2b= 0,5.2= 1$ (2)
(1)(2) => $a=b=0,2$
$\%m_{Al}= \frac{0,2.27.100}{18,4}= 29,35\%$
=> $\%m_{Zn}= 70,65\%$
