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Bài 2. Cho 8g Fe2O3 tác dụng vừa đủ với dd HCl 20% (D = 1,1g/ml). Hãy tính: a. Thể tích dd HCl đã dùng b. Nồng độ % dd thu được sau phản ứng
a) \(n_{Fe_2O_3}=0,05\left(mol\right)\)
\(Fe_2O_3+6HCl\rightarrow2FeCl_3+3H_2O\)
\(n_{HCl}=6n_{Fe_2O_3}=0,3\left(mol\right)\)
=> \(m_{ddHCl}=\dfrac{0,3.36,5}{20\%}=54,75\left(g\right)\)
=> \(V_{HCl}=\dfrac{m}{D}=\dfrac{54,75}{1,1}=49,77\left(g\right)\)
b) \(m_{ddsaupu}=8+54,75=62,75\left(g\right)\)
\(C\%_{FeCl_3}=\dfrac{0,05.2.162,5}{62,75}.100=25,9\%\)
PTHH: \(Fe_2O_3+6HCl\rightarrow2FeCl_3+3H_2O\)
Ta có: \(n_{HCl}=0,2\cdot3=0,6\left(mol\right)\)
\(\Rightarrow\left\{{}\begin{matrix}n_{FeCl_3}=0,2\left(mol\right)\\n_{Fe_2O_3}=0,1\left(mol\right)\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}m_{Fe_2O_3}=0,1\cdot160=16\left(g\right)\\m_{FeCl_3}=0,2\cdot162,5=32,5\left(g\right)\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}C\%_{FeCl_3}=\dfrac{32,5}{16+200\cdot1,1}\cdot100\%\approx13,77\%\\C_{M_{FeCl_3}}=\dfrac{0,2}{0,2}=1\left(M\right)\end{matrix}\right.\)
a)%mZnO=20% => %mCuO=100% - 20%=80%
b) mZnO=20%.25=5(g)=> nZnO=5/81(mol)
mCuO=25-5=20(g) => nCuO=20/80=0,25(mol)
PTHH: ZnO +2 HCl -> ZnCl2 + H2O
5/81_______10/81___5/81(mol)
CuO +2 HCl -> CuCl2 + H2O
0,25__0,5______0,25(mol)
=> nHCl=10/81 + 0,5=101/162(mol)
=>mHCl= 101/162 . 36,5=7373/324(g)
=> mddHCl= 7373/324 : 15%= 151,708(g)
=> VddHCl= 151,708/1,1=137,916(ml)
\(n_{Zn}=\dfrac{4,55}{65}=0,07(mol)\\ Zn+2HCl\to ZnCl_2+H_2\\ a,n_{HCl}=0,14(mol)\\ \Rightarrow C_{M_{HCl}}=\dfrac{0,14}{0,2}=0,7M\\ b,n_{H_2}=0,07(mol)\\ \Rightarrow V_{H_2}=0,07.22,4=1,568(l)\\ c,n_{ZnCl_2}=0,07(mol)\\ \Rightarrow m_{ZnCl_2}=0,07.136=9,52(g)\\ c,ZnCl_2+2AgNO_3\to 2AgCl\downarrow+Zn(NO_3)_2\)
\(m_{dd_{ZnCl_2}}=200.0,8+4,55-0,07.2=164,41(g)\\ n_{AgCl}=0,14(mol);n_{Zn(NO_3)_2}=0,07(mol)\\ \Rightarrow C\%_{Zn(NO_3)_2}=\dfrac{0,07.189}{164,41+200-0,14.143,5}.100\%=3,84%\)
PTHH: \(ZnO+2HCl\rightarrow ZnCl_2+H_2O\)
\(CuO+2HCl\rightarrow CuCl_2+H_2O\)
Ta có: \(\%m_{ZnO}=20\%\) \(\Rightarrow\%m_{CuO}=80\%\)
Mặt khác: \(\left\{{}\begin{matrix}n_{Zn}=\dfrac{25\cdot20\%}{81}=\dfrac{5}{81}\left(mol\right)\\n_{CuO}=\dfrac{25\cdot80\%}{80}=0,25\left(mol\right)\end{matrix}\right.\)
\(\Rightarrow n_{HCl}=\left(\dfrac{5}{81}+0,25\right)\cdot2=\dfrac{101}{162}\left(mol\right)\)
\(\Rightarrow m_{ddHCl}=\dfrac{\dfrac{101}{162}\cdot36,5}{15\%}\approx151,71\left(g\right)\) \(\Rightarrow V_{ddHCl}=\dfrac{151,71}{1,1}\approx137,92\left(ml\right)\)
