Trộn lẫn 100ml dd K2CO3 0,5M với 100ml dd CaCl2 0,1M.
a. Tính khối lượng kết tủa thu được.
b. Tính CM các ion trong dd sau phản ứng
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PTHH: \(Na_2SO_4+CaCl_2\rightarrow2NaCl+CaSO_4\downarrow\)
Ta có: \(\left\{{}\begin{matrix}n_{Na_2SO_4}=0,1\cdot0,5=0,05\left(mol\right)\\n_{CaCl_2}=0,1\cdot0,4=0,04\left(mol\right)\end{matrix}\right.\) \(\Rightarrow\) Na2SO4 dư
\(\Rightarrow\left\{{}\begin{matrix}n_{CaSO_4}=0,04\left(mol\right)\\n_{NaCl}=0,08\left(mol\right)\\n_{Na_2SO_4\left(dư\right)}=0,01\left(mol\right)\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}m_{CaSO_4}=0,04\cdot136=5,44\left(g\right)\\C_{M_{NaCl}}=\dfrac{0,08}{0,1+0,1}=0,4\left(M\right)\\C_{M_{Na_2SO_4\left(dư\right)}}=\dfrac{0,01}{0,2}=0,05\left(M\right)\end{matrix}\right.\)
\(n_{Ca^{2+}}=0.1\cdot0.4=0.04\left(mol\right),n_{Ba^{2+}}=0.1\cdot0.2=0.02\left(mol\right)\)
\(n_{CO_3^{2-}}=0.2\cdot0.3+0.2\cdot0.1=0.08\left(mol\right)\)
\(Ca^{2+}+CO_3^{2-}\rightarrow CaCO_3\)
\(0.04.......0.04.......0.04\)
\(Ba^{2+}+CO_3^{2-}\rightarrow BaCO_3\)
\(0.02.......0.02.......0.02\)
\(m_{\downarrow}=0.04\cdot100+0.02\cdot197=7.94\left(g\right)\)
Sửa đề H2SO2 thành H2SO4
\(n_{Ba^{2+}}=n_{Ba\left(OH\right)2}=0,01.0,1=0,001\left(mol\right)\)
\(\Rightarrow n_{OH^-}=2n_{Ba\left(OH\right)2}=2.0,001=0,002\left(mol\right)\)
\(n_{SO_4^{2-}}=n_{H2SO4}=0,1.0,05=0,005\left(mol\right)\)
\(\Rightarrow n_{H^+}=2n_{H2SO4}=2.0,005=0,01\left(mol\right)\)
\(Ba^{2+}+SO_4^{2-}\rightarrow BaSO_4\)
0,001 0,01 0,01
Xét tỉ lệ : \(0,001< 0,01\Rightarrow SO_4^{2-}dư\)
\(n_{Ba^{2+}\left(pư\right)}=n_{BaSO4}=0,001\left(mol\right)\Rightarrow m_{BaSO4}=0,001.233=0,233\left(g\right)\)
\(H^++OH^-\rightarrow H_2O\)
0,01 0,002
Xét tỉ lệ : \(0,01>0,002\Rightarrow H^+dư\)
\(n_{H^+dư}=0,01-0,002=0,008\left(mol\right)\Rightarrow\left[H^+\right]=\dfrac{0,008}{0,1+0,1}=0,04M\)
\(\Rightarrow pH=-log\left(0,04\right)\approx1,4\)
PTHH: \(Na_2CO_3+Ca\left(OH\right)_2\rightarrow2NaOH+CaCO_3\downarrow\)
Ta có: \(\left\{{}\begin{matrix}n_{Na_2CO_3}=0,1\cdot1=0,1\left(mol\right)\\n_{Ca\left(OH\right)_2}=0,1\cdot1,5=0,15\left(mol\right)\end{matrix}\right.\) \(\Rightarrow\) Ca(OH)2 dư
\(\Rightarrow\left\{{}\begin{matrix}n_{NaOH}=0,2\left(mol\right)\\n_{CaCO_3}=0,1\left(mol\right)\\n_{Ca\left(OH\right)_2\left(dư\right)}=0,05\left(mol\right)\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}m_{CaCO_3}=0,1\cdot100=10\left(g\right)\\C_{M_{NaOH}}=\dfrac{0,2}{0,2}=1\left(M\right)\\C_{M_{Ca\left(OH\right)_2}}=\dfrac{0,05}{0,2}=0,25\left(M\right)\end{matrix}\right.\)
nNa2CO3= 0,1(mol) ; nCa(OH)2=0,15(mol)
a) PTHH: Na2CO3 + Ca(OH)2 -> CaCO3 + 2 NaOH
Vì: 0,1/1 < 0,15/1
=> Na2CO3 hết, Ca(OH)2 dư, tính theo Na2CO3.
=> nCaCO3=nCa(OH)2 (p.ứ)=nNa2CO3= 0,1(mol)
=>m(kết tủa)=mCaCO3=0,1.100=10(g)
b) Vddsau= 100+100=200(ml)=0,2(l)
nNaOH=2.0,1=0,2(mol)
nCa(OH)2(dư)=0,15-0,1=0,05(mol)
=>CMddNaOH=0,2/0,2= 1(M)
CMddCa(OH)2 (dư)= 0,05/ 0,2=0,25(M)
\(n_{K_2CO_3}=0.1\cdot0.5=0.05\left(mol\right)\)
\(n_{CaCl_2}=0.1\cdot0.1=0.01\left(mol\right)\)
\(K_2CO_3+CaCl_2\rightarrow CaCO_3+2KCl\)
Lập tỉ lệ :
\(\dfrac{0.05}{1}>\dfrac{0.01}{1}\) \(\Rightarrow K_2CO_3dư\)
\(n_{CaCO_3}=n_{CaCl_2}=0.01\left(mol\right)\)
\(m=0.01\cdot100=1\left(g\right)\)
\(b.\)
Các chất có trong dung dịch :
\(K_2CO_3\left(dư\right):0.04\left(mol\right),KCl:0.02\left(mol\right)\)
\(V=0.1+0.1=0.2\left(l\right)\)
\(\left[K^+\right]=\dfrac{0.04\cdot2+0.02}{0.2}=0.5\left(M\right)\)
\(\left[CO_3^{2-}\right]=\dfrac{0.04}{0.2}=0.2\left(M\right)\)
\(\left[Cl^-\right]=\dfrac{0.02}{0.2}=0.1\left(M\right)\)