1, 

$\text{Số nguyên tử O là: 4. 3 = 12 nguyên tử}$

2, $\text{5 hợp chất: $NaOH_{}$ ; $CO_{2}$ ; MgO ; FeO ; HCl}$

3, $\text{$n_{CuO}$ = $\dfrac{m}{M}$ = $\dfrac{16}{80}$ = 0,2 mol}$

4, $\text{$n_{CO_2}$ = $\dfrac{V}{22,4}$ = $\dfrac{2,24}{22,4}$ = 0,2 mol}$

$\text{$m_{CO_2}$ = n. M = 0,1 . 44 = 4,4 gam}$

5, $\text{$M_{NaOH}$ = 23 + 16 + 1 = 40 g/mol}$

6, $\text{PTK $Fe_{2}$$(SO_{4}$$)_{3}$ = 56. 2 + 3. (32+ 16.4) = 400 đvC}$

7, $\text{Số nguyên tử = n. N = 0,35. 2. 6. $10^{23}$ = 4,2. $10^{23}$ nguyên tử }$

8, $\text{7 đơn chất: Na, Mg, S, Fe, Ba, Cu, Ag}$

9, $\text{$V_{H_2(đktc)}$ = n. 22,4 = 0,3. 22,4 = 6,72 lít}$

$\text{#Kudo}$