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Bài 1:
Ta có: \(\Sigma n_{OH^-}=n_{NaOH}+2n_{Ba\left(OH\right)_2}=0,05.0,01+0,05.0,005.2=0,001\left(mol\right)\)
\(n_{H^+}=n_{HCl}=0,05.0,015=0,00075\left(mol\right)\)
PT ion: \(OH^-+H^+\rightarrow H_2O\)
______0,001__0,00075 (mol)
⇒ OH- dư. nOH- (dư) = 2,5.10-4 (mol)
\(\Rightarrow\left[OH^-\right]=\frac{2,5.10^{-4}}{0,1}=2,5.10^{-3}M\Rightarrow\left[H^+\right]=4.10^{-12}M\)
\(\Rightarrow pH\approx11,4\)
Bài 2: Đáp án D
Giải:
Ta có: \(\Sigma n_{H^+}=n_{HCl}+2n_{H_2SO_4}=0,1.0,002+0,2.2.x=2.10^{-4}+0,4x\left(mol\right)\)
\(\Rightarrow\left[H^+\right]=\frac{2.10^{-4}+0,4x}{0,3}M\)
\(\Rightarrow pH=-log\left(\frac{2.10^{-4}+0,4x}{0,3}\right)=2,7\)
\(\Rightarrow x\approx9,964.10^{-4}\approx10^{-3}\)
Bạn tham khảo nhé!
n\(_{Ba\left(OH\right)_2}=0,1.0,5=0,05\left(mol\right)\)
\(Ba\left(OH\right)_2\rightarrow Ba^{2+}+2OH^-\)
0,05 0,05 0,1 (mol)
\(n_{KOH}=0,1.0,5=0,05\left(mol\right)\)
\(KOH\rightarrow K^++OH^-\)
0,05 0,05 0,05 (mol)
\(\left[H^+\right]=0,1-0,05=0,05\left(mol\right)\)
\(C_MH^+=\dfrac{0,05}{0,2}=0,25\left(M\right)\)
\(\rightarrow PH=0,6020599913\simeq0,6\)
\(n_{H^+}=\left[H^+\right].V=10^{-1}.0,1=0,01\left(mol\right)\)
\(n_{OH^-}=0,1a\left(mol\right)\)
\(n_{OH^-\text{ dư}}=\left[OH^-\right].V=10^{-2}.\left(0,1+0,1\right)=0,002\left(mol\right)\)
Ta có:
\(n_{OH^-}-n_{OH^-\text{ dư}}=n_{H^+}\)
\(\Leftrightarrow0,1a-0,002=0,01\)
\(\Leftrightarrow a=0,12\)
\([H^{+}]=0,1M\\ \Rightarrow n_{H^{+}}=0,1.0,1=0,01(mol)\\ pH=12 \to pOH=14-12=2\\ \Rightarrow [OH^{-}]=0,01\\ \Rightarrow n_{OH^{-}}=0,002(mol)\\ H^{+} +OH^{-} \to H_2O\\ n_{NaOH}=0,01+0,002=0,012(mol)\\ \Rightarrow a=0,12M\)
- Số mol NaOH=0,2a
-Số mol Ba(OH)2=0,2a
- Tổng số mol OH-=0,6a
\(\left[OH^-\right]=\dfrac{0,6a}{0,3}=2a\left(M\right)\)
pH=14+lg\(\left[OH^-\right]\)suy ra: 13=14+lg\(\left[OH^-\right]\)suy ra:
lg\(\left[OH^-\right]\)=-1 suy ra: \(\left[OH^-\right]\)=10-1=0,1M. Vậy:
2a=0,1 suy ra: a=0,05M
- Số mol OH-=0,6a=0,6.0.05=0,03mol
- Số mol H+=0,175.0,2.2=0,07mol
H++OH-\(\rightarrow\)H2O
- Số mol H+ dư= 0,07-0,03=0,04mol
- Tổng thể tích=100+200+200=500ml=0,5 lít
\(\left[H^+\right]=\dfrac{0,04}{0,5}=0,08\left(M\right)\)
pH=-lg\(\left[H^+\right]\)=-lg(0,08)\(\approx\)1,1
Ta có: \(n_{H^+}=2n_{H_2SO_4}=2.0,1.0,005=0,001\left(mol\right)\)
\(n_{OH^-}=n_{KOH}=0,1.0,012=0,0012\left(mol\right)\)
PT ion: \(H^++OH^-\rightarrow H_2O\)
_____0,001_0,0012________ (mol)
⇒ OH- dư.
\(\Rightarrow n_{OH^-\left(dư\right)}=0,0002\left(mol\right)\)
\(\Rightarrow\left[OH^-\right]_{\left(dư\right)}=\frac{0,0002}{0,1+0,1}=0,001M\)
\(\Rightarrow\left[H^+\right]=\frac{10^{-14}}{0,001}=10^{-11}M\)
\(\Rightarrow x=pH=11\)
Bạn tham khảo nhé!