a,
Xét $1l$ dung dịch
$m_{dd}=1000.1,1=1100g$
$\to n_{CH_3COOH}=\dfrac{1100.18\%}{60}=3,3(mol)$
$\to C_{CH_3COOH}=\dfrac{3,3}{1}=3,3M$
$CH_3COOH\rightleftharpoons CH_3COO^-+H^+$
$\alpha=2\%\to C_{CH_3COOH\text{phân li}}=3,3.2\%=0,066M=[H^+]=[CH_3COO^-]$
$\to [CH_3COOH]=3,3-0,066=3,234M$
$pH=-\log[H^+]=1,18$
$K_a=\dfrac{[H^+][CH_3COO^-]}{[CH_3COOH]}=1,3469.10^{-3}$
b,
Xét $1l$ dung dịch
$m_{dd}=1000.1,2=1200g$
$\to n_{HF}=\dfrac{1200.15\%}{20}=9(mol)$
$\to C_{HF}=\dfrac{9}{1}=9M$
$HF\rightleftharpoons H^++F^-$
$\alpha=4\%\to C_{HF\text{phân li}}=9.4\%=0,36M=[H^+]=[F^-]$
$\to [HF]=9-0,36=8,64M$
