$n_{NaOH} = 0,001(mol)$
$n_{Ba(OH)_2} = 0,01.0,15 = 0,0015(mol)$

$NaOH \to Na^+ + OH^-$
$Ba(OH)_2 \to Ba^{2+} + 2OH^-$

Ta có : 

$n_{OH^-}= 0,001 + 0,0015.2 = 0,004(mol)$
$V_{dd} = 0,1 + 0,15 = 0,25(mol)$
$[OH^-] = \dfrac{0,004}{0,25} = 0,016M$

$pOH = -log(0,016) = 1,795 \Rightarrow pH = 14 - 1,795 = 12,205$

e cảm ơn ạ 🥰

nHCl =0,002 mol
nH2SO4 = 0,001 mol
=> n[H+] = 0,002+0,002=0,004 mol
V dd =0,3 l
=> p[H+]=1,88

a, \(\left\{{}\begin{matrix}n_{Ba^{2+}}=4.10^{-3}\left(mol\right)\\n_{Na^+}=3.10^{-3}\left(mol\right)\\n_{OH^-}=0,011\left(mol\right)\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}\left[Ba^{2+}\right]=\dfrac{4.10^{-3}}{0,2+0,3}=0,008M\\\left[Na^+\right]=\dfrac{3.10^{-3}}{0,2+0,3}=0,006M\\\left[OH^-\right]=\dfrac{0,011}{0,2+0,3}=0,022M\end{matrix}\right.\)

b, Để trung hòa dung dịch A thì:

\(n_{H^+}=n_{OH^-}\)

\(\Leftrightarrow0,01.V_{ddHCl}=\left(0,02.2+0,01\right).0,2\)

\(\Leftrightarrow V_{ddHCl}=1\left(l\right)\)

cần lời giải chi tiết ạ

Ví dụ 5 :

n KOH = 0,02.0,35 = 0,007(mol)

n HCl = 0,08.0,1 = 0,008(mol)

$KOH + HCl \to KCl + H_2O$

n HCl pư = n KOH = 0,007(mol)

=> n HCl dư = 0,008 - 0,007 = 0,001(mol)

V dd = 0,02 + 0,08 = 0,1(mol)

=> [H⁺ ] = CM HCl dư = 0,001/0,1 = 0,01M

=> pH = -log(0,01) = 2

Ví dụ 3  :

n NaOH = 0,01.0,001V(mol)

n HCl = 0,03.0,001V(mol)

$HCl + NaOH \to NaCl + H_2O$

n HCl dư = 0,03.0,001V - 0,01.0,001V = 0,02.0,001V(mol)

Suy ra : 

[H⁺ ] = CM HCl dư = 0,02.0,001V/0,002V = 0,01(M)

=> pH = -log(0,01) = 2

\(n_{HCl}=0.1\cdot0.03=0.003\left(mol\right)\)

\(n_{NaOH}=0.1\cdot0.01=0.001\left(mol\right)\)

\(NaOH+HCl\rightarrow NaCl+H_2O\)

Lập tỉ lệ : 

\(\dfrac{0.003}{1}>\dfrac{0.001}{1}\Rightarrow HCldư\)

\(n_{HCl\left(dư\right)}=0.003-0.001=0.002\left(mol\right)\)

\(\left[H^+\right]=\dfrac{0.002}{0.1+0.1}=0.01\)

\(pH=-log\left(0.01\right)=2\)

\(b.\)

\(Ba\left(OH\right)_2+2HCl\rightarrow BaCl_2+2H_2O\)

\(0.001..........0.002\)

\(V_{Ba\left(OH\right)_2}=\dfrac{0.001}{1}=0.001\left(l\right)\)