Câu 2:

NaOH 2,4M có $V_1$ ml

$n_1 = C_{M1} . V_1 = 2,4 . \frac{V_1}{1000} mol$

NaOH 1M có $V_2 = 650 ml$

$n_2 = C_{M2} . V_2 = 1 . \frac{650}{1000}=0,65 mol$

NaOH 1,6M có $V_{\text{tổng}}= V_1 + V_2 = V_1 + 650 ml$

$n_{\text{tổng}} = C_{M3} . V_{\text{tổng}} = 1,6 . \frac{(V_1 + 650)}{1000} mol$

mà $n_{\text{tổng}} = n_1 + n_2$

$\rightarrow  1,6 . \frac{(V_1 + 650)}{1000} = 2,4 . \frac{V_1}{1000} + 0,65$

$\rightarrow V_1 = 487,5 ml

Câu 4

$CuCl_2$ 1,2M có $V_1$ ml

$n_1 = C_{M1} . V_1 = 1,2 . \frac{V_1}{1000} mol$

$CuCl_2$ 4M có $V_2 = 220 ml$

$n_2 = C_{M2} . V_2 = 4 . \frac{220}{1000}=0,88 mol$

$CuCl_2$ 2M có $V_{\text{tổng}}= V_1 + V_2 = V_1 + 220 ml$

$n_{\text{tổng}} = C_{M3} . V_{\text{tổng}} = 2 . \frac{(V_1 + 220)}{1000} mol$

mà $n_{\text{tổng}} = n_1 + n_2$

$\rightarrow  2 . \frac{(V_1 + 220)}{1000} = 1,2 . \frac{V_1}{1000} + 0,88$

$\rightarrow V_1 = 550 ml$