$\text{Câu 1:}$
$\text{Đặt CTHH: $Na_{x}O_{y}$}$
$\text{Theo QTHH: ax = by ⇔ x/y = b/a = II/I = 2/1}$
$\text{⇒ CTHH: $Na_{2}O$}$
$\text{Đặt CTHH: $Al_{x}Cl_{y}$}$
$\text{Theo QTHT: ax = by ⇔ x/y = b/a = I/III = 1/3}$
$\text{⇒ CTHH: $AlCl_{3}$}$
$\text{Đặt CTHH: $S_{x}O_{y}$}$
$\text{Theo QTHT: ax = by ⇔ x/y = b/a = II/VI = 1/3}$
$\text{⇒ CTHH: $SO_{3}$}$
$\text{Đặt CTHH: $Cu_{x}(NO_{3})_{y}$}$
$\text{Theo QTHT: ax = by ⇔ x/y = b/a = I/II =1/2}$
$\text{⇒ CTHH: $Cu(NO_{3})_{2}$}$
$\text{Câu 2:}$
$\text{- $NaSO_{4}$ → $Na_{2}SO_{4}$: natri sunfat}$
$\text{- $Ba(SO3)_{2}$ → $BaSO_{3}$: bari sunfit}$
$\text{- $KCO_{3}$ → $K_{2}CO_{3}$: kali cacbonat}$
$\text{- $Fe_{2}O$ → $FeO_{ }$ hoặc $Fe_{2}O_{3}$: sắt (II) hoặc (III) oxit}$
$\text{- $P_{5}O_{2}$ → $P_{2}O_{5}$: điphotpho pentaoxit}$
$\text{- $CaOH_{ }$ → $Ca(OH)_{2}$: canxi hiđroxit}$
$\text{- $K_{2}NO_{3}$ → $KNO_{3}$: kali nitrat}$
$\text{- $NH_{4}Cl_{2}$ → $NH_{4}Cl$: amoni clorua}$
$\text{- $H_{2}PO_{4}$ → $H_{3}PO_{4}$: axit photphoric}$
$\text{- $Cu(OH)_{2}$: đồng (II) hiđroxit}$
$\text{- $Al_{2}O_{3}$: nhôm oxit}$
