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a, \(n_{HCl}=0,1.0,2=0,02\left(mol\right)=n_{H^+}=n_{Cl^-}\)
\(n_{H_2SO_4}=0,1.0,2=0,02\left(mol\right)=n_{SO_4^{2-}}\) \(\Rightarrow n_{H^+}=2n_{H_2SO_4}=0,04\left(mol\right)\)
\(n_{NaOH}=0,3.0,4=0,12\left(mol\right)=n_{Na^+}=n_{OH^-}\)
\(\Rightarrow\sum n_{H^+}=0,02+0,04=0,06\left(mol\right)\)
\(H^++OH^-\rightarrow H_2O\)
0,06__0,06 (mol)
⇒ nOH- dư = 0,12 - 0,06 = 0,06 (mol)
\(\Rightarrow\left\{{}\begin{matrix}\left[Cl^-\right]=\dfrac{0,02}{0,1+0,3}=0,05\left(M\right)\\\left[SO_4^{2-}\right]=\dfrac{0,02}{0,1+0,3}=0,05\left(M\right)\\\left[Na^+\right]=\dfrac{0,12}{0,1+0,3}=0,3\left(M\right)\\\left[OH^-\right]=\dfrac{0,06}{0,1+0,3}=0,15\left(M\right)\end{matrix}\right.\)
b, pH = 14 - (-log[OH-]) ≃ 13,176
a, \(\left[Na^+\right]=0,1\)
\(\left[K^+\right]=0,1\)
\(\left[OH^-\right]=0,2\)
\(\left[SO_4^{2-}\right]=0,2\)
\(\left[H^+\right]=0,4\)
b, \(n_{H^+}=0,1.0,4=0,04\left(mol\right)\)
\(n_{OH^-}=0,1.0,2=0,02\left(mol\right)\)
\(H^++OH^-\rightarrow H_2O\)
\(\Rightarrow n_{H^+dư}=0,02\left(mol\right)\)
\(\Rightarrow\left[H^+\right]=\dfrac{0,02}{200}=10^{-4}\)
\(\Rightarrow pH=4\)
$n_{NaOH} = n_{KOH} = 0,1.0,1 = 0,01(mol)$
$n_{H_2SO_4} = 0,02(mol)$
OH- + H+ → H2O
Bđ : 0,01...0,04..................(mol)
Pư : 0,01...0,01...................(mol)
Sau pư : 0......0,03...................(mol)
$V_{dd} = 0,1 + 0,1 = 0,2(lít)$
Vậy :
$[K^+] = [Na^+] = \dfrac{0,01}{0,2} = 0,05M$
$[H^+] = \dfrac{0,03}{0,2} = 0,15M$
$[SO_4^{2-}] = \dfrac{0,02}{0,2} = 0,1M$
b)
$pH = -log(0,15) = 0,824$
Chọn D
Trộn 3 dung dịch với thể tích bằng nhau thu được 150 ml dung dịch X → mỗi dung dịch lấy 50ml.
→ n H + = 0,05.0,2 + 0,05.2.0,1 + 0,05.0,08 = 0,024 mol.
`100mL=0,1L`
`n_{H^+}=0,1.0,05.2+0,1.0,1=0,02(mol)`
`n_{SO_4^{2-}}=0,1.0,05=0,005(mol)`
`n_{OH^-}=0,1.0,2+0,1.0,1.2=0,04(mol)`
`n_{Ba^{2+}}=0,1.0,1=0,01(mol)`
`Ba^{2+}+SO_4^{2-}->BaSO_4`
Do `0,01>0,005->` Tính theo `SO_4^{2-}`
`n_{BaSO_4}=n_{SO_4^{2-}}=0,005(mol)`
`->m_↓=0,005.233=1,165(g)`
`H^{+}+OH^{-}->H_2O`
Do `0,02<0,04->OH^-` dư
`n_{OH^{-}\ pu}=n_{H^+}=0,02(mol)`
`->n_{OH^{-}\ du}=0,04-0,02=0,02(mol)`
Trong X: `[OH^-]={0,02}/{0,1+0,1}=0,1M`
`->pH=14-pOH=14+lg[OH^-]=13`
a, \(n_{NaOH}=0,15.0,2=0,03\left(mol\right)=n_{Na^+}=n_{OH^-}\)
\(n_{KOH}=0,15.0,2=0,03\left(mol\right)=n_{K^+}=n_{OH^-}\)
⇒ ΣnOH- = 0,03 + 0,03 = 0,06 (mol)
\(n_{HCl}=0,25.0,4=0,1\left(mol\right)=n_{H^+}=n_{Cl^-}\)
\(H^++OH^-\rightarrow H_2O\)
0,06____0,06 (mol) ⇒ nH+ dư = 0,1 - 0,06 = 0,04 (mol)
\(\left[Na^+\right]=\left[K^+\right]=\dfrac{0,03}{0,15+0,25}=0,075\left(M\right)\)
\(\left[H^+\right]=\dfrac{0,04}{0,15+0,25}=0,1\left(M\right)\)
\(\left[Cl^-\right]=\dfrac{0,1}{0,15+0,25}=0,25\left(M\right)\)
b, pH = -log[H+] = 1