Trộn lẫn 3 dd H3PO4 6%(D=1,03g/ml); H3PO4 4%(D=1,02g/ml); H3PO4 4%(D=1,01g/ml) theo tỉ lệ 1:3:2. Xác định nồng độ mol của dung dịch thu được.
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(b.n_{NaOH\left(tổng\right)}=0,4.0,5+\dfrac{100.1,33.20\%}{40}=0,865\left(mol\right)\\ \left[Na^+\right]=\left[OH^-\right]=\left[NaOH\left(sau\right)\right]=\dfrac{0,865}{0,4+0,1}=1,73\left(M\right)\\ c.n_{HCl}=0,05.0,12=0,006\left(mol\right)\\ n_{HNO_3}=0,15.0,1=0,015\left(mol\right)\\ \left[H^+\right]=\dfrac{0,006+0,015}{0,05+0,15}=0,105\left(M\right)\\ \left[NO^-_3\right]=\dfrac{0,015}{0,05+0,15}=0,075\left(M\right)\\ \left[Cl^-\right]=\dfrac{0,006}{0,05+0,15}=0,03\left(M\right)\)
\(d.n_{H_2SO_4}=0,4.0,05=0,02\left(mol\right)\\ n_{HCl}=0,35.0,2=0,07\left(mol\right)\\ \left[H^+\right]=\dfrac{0,02.2+0,07}{0,05+0,35}=0,275\left(M\right)\\ \left[SO^{2-}_4\right]=\dfrac{0,02}{0,05+0,35}=0,05\left(M\right)\\ \left[Cl^-\right]=\dfrac{0,07}{0,05+0,35}=0,175\left(M\right)\\ f.n_{KOH}=\dfrac{20.1,31.32\%}{56}=\dfrac{131}{875}\left(mol\right)\\ n_{Ba\left(OH\right)_2}=0,08.1=0,08\left(mol\right)\\ \left[OH^-\right]=\dfrac{\dfrac{131}{875}+0,08.2}{0,02+0,08}=\dfrac{542}{175}\left(M\right)\\ \left[Ba^{2+}\right]=\dfrac{0,08}{0,02+0,08}=0,8\left(M\right)\)
\(\left[K^+\right]=\dfrac{\dfrac{131}{875}}{0,02+0,08}=\dfrac{262}{175}\left(M\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
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
![](https://rs.olm.vn/images/avt/0.png?1311)
\(n_{HCl.5M}=0,05\times5=0,25\left(mol\right)\)
\(m_{ddHCl.30\%}=200\times1,33=266\left(g\right)\)
\(\Rightarrow m_{HCl.30\%}=266\times30\%=79,8\left(g\right)\)
\(\Rightarrow n_{HCl.30\%}=\frac{79,8}{36,5}=\frac{798}{365}\left(mol\right)\)
\(\Rightarrow\Sigma n_{HCl}mới=0,25+\frac{798}{365}=\frac{3557}{1460}\left(mol\right)\)
\(\Sigma V_{ddHCl}mới=50+200=250\left(ml\right)=0,25\left(l\right)\)
\(\Rightarrow C_{M_{HCl}}mới=\frac{3557}{1460}\div0,25=9,75\left(M\right)\)