Câu `3 :`
Ta có PT: `\text{Zn} + \text{2 HCl} → \text{ZnCl}_2 + \text{H2} ↑`
`=> \text{n}_\text{HCl} = 2 \text{n}_\text{Zn} = 2 . 0,05 = 0,1 \text{(mol)}`
Chọn câu `\mathbb{A}`
Câu `4 :`
Ta có PT: `\text{CuO} + \text{H}_2\text{SO4} → \text{CuSO}_4 + \text{H}_2\text{O}`
`=> \text{n}_\text{CuO} = \text{n}_\text{H2SO4} = 0,25 \text{(mol)}`
Chọn câu `\mathbb{A}`
