Đáp án:
$7/$
$Mg+2HCl→MgCl_2+H_2$
Tl: $1:2:1:1$
$b/$
BTKL:
$m_{Mg}+m_{HCl}=m_{MgCl_2}+m_{H_2}$
$⇒m_{MgCl_2}=16,9(g)$
$8/$
$a/$
$4K+O_2→2K_2O$
TL: $4:1:2$
$b/$
BTKL:
$m_K+m_{O_2}=m_{K_2O}$
$⇒m_{K_2O}=1,9(g)$
$9/$
$a/$
$4Na+O_2→2Na_2O$
TL: $4:1:2$
$b/$
BTKL:
$m_{Na}+m_{O_2}=m_{Na_2O}$
$⇒m_{O_2}=3(g)$