1.
a, $2KNO_3\buildrel{{t^o}}\over\to 2KNO_2+O_2$
b, $Na_2CO_3+2HCl\to 2NaCl+CO_2+H_2O$
c, $3Ca+2P\buildrel{{t^o}}\over\to Ca_3P_2$
d, $Si+O_2\buildrel{{t^o}}\over\to SiO_2$
2.
$n_{NO_2}=\dfrac{336.10^{-3}}{22,4}=0,015(mol)$
Bảo toàn e: $2n_{Mg}=n_{NO_2}$
$\to n_{Mg}=0,0075(mol)$
$\to m=0,0075.24=0,18g$