`n_(NaOH) = 30 / 40 = 0.75 ( mol ) `
`PT : MgCl_2 + 2NaOH -> 2NaCl + Mg(OH)_2 ↓`
` 0.375 - 0.75 - 0.75 - 0.375 ( mol ) `
* Kết tủa là : `Mg(OH)_2`
* Nung : ` PT :` ` Mg(OH)_2 \overset{t^o}to\ MgO + H_2O`
` 0.375 - 0.375 ( mol ) `
`b) m_(MgO) = 0.375 * 40 = 15 ( g )`
` CM_(MgCl_2) = 0.375 / 0.5 = 0.75 M`