Câu 8:
a,
$n_{H^+}=n_{HCl}+n_{HNO_3}=0,1.0,1+0,2.0,05=0,02(mol)$
$n_{Cl^-}=n_{HCl}=0,1.0,1=0,01(mol)$
$n_{NO_3^-}=n_{HNO_3}=0,2.0,05=0,01(mol)$
$V_{dd}=0,1+0,2=0,3l$
$\Rightarrow [H^+]=\dfrac{0,02}{0,3}=\dfrac{1}{15}(M), [Cl^-]=[NO_3^-]=\dfrac{0,01}{0,3}=\dfrac{1}{30}(M)$
b,
$pH=-\lg\dfrac{1}{15}=1,18$
Câu 9:
$n_{OH^-}=n_{NaOH}=0,2.0,1=0,02(mol)$
$n_{H^+}=n_{HCl}=0,3.0,2=0,06(mol)$
$\Rightarrow n_{H^+\text{dư}}=0,06-0,02=0,04(mol)$
$V_{dd}=0,2+0,3=0,5l$
$\to pH=-\lg\dfrac{0,04}{0,5}=1,1$
