Câu 1 : 

\(n_{Mg}=\dfrac{8.4}{24}=0.35\left(mol\right)\)

\(Mg+2HCl\rightarrow MgCl_2+H_2\)

\(0.35.......0.7.........0.35..........0.35\)

\(C\%_{HCl}=\dfrac{0.7\cdot36.5}{146}\cdot100\%=17.5\%\)

\(m_{\text{dung dịch sau phản ứng}}=8.4+146-0.35\cdot2=153.7\left(g\right)\)

\(C\%_{MgCl_2}=\dfrac{0.35\cdot95}{153.7}\cdot100\%=21.6\%\)

Câu 2 :

\(n_{CaCO_3}=\dfrac{10}{100}=0.1\left(mol\right)\)

\(n_{HCl}=\dfrac{114.1\cdot8\%}{36.5}=0.25\left(mol\right)\)

\(CaCO_3+2HCl\rightarrow CaCl_2+CO_2+H_2O\)

\(1................2\)

\(0.1.............0.25\)

\(LTL:\dfrac{0.1}{1}< \dfrac{0.25}{2}\Rightarrow HCldư\)

\(m_{\text{dung dịch sau phản ứng}}=10+114.1-0.1\cdot44=119.7\left(g\right)\)

\(C\%_{HCl\left(dư\right)}=\dfrac{\left(0.25-0.2\right)\cdot36.5}{119.7}\cdot100\%=1.52\%\)

\(C\%_{CaCl_2}=\dfrac{0.2\cdot111}{119.7}\cdot100\%=18.54\%\)

Câu 3 : 

\(n_{H_2}=\dfrac{6.72}{22.4}=0.3\left(mol\right)\)

\(Fe+2HCl\rightarrow FeCl_2+H_2\)

\(0.3.......0.6......................0.3\)

\(m_{Fe}=0.3\cdot56=16.8\left(g\right)\)

\(m_{dd_{HCl}}=150\cdot1.2=180\left(g\right)\)

\(C\%_{HCl}=\dfrac{0.6\cdot36.5}{180}\cdot100\%=12.16\%\)

\(C_{M_{HCl}}=\dfrac{0.6}{0.15}=4\left(M\right)\)

nCaCO3=10100=0,1molnCaCO3=10100=0,1mol, nHCl=mdd.C%36,5.100=114,1.836,5.100=0,25molnHCl=mdd.C%36,5.100=114,1.836,5.100=0,25mol

CaCO3 + 2HCl  →CaCl2+ CO2↑ + H2O

Ta có: 0,11<0,2520,11<0,252 → CaCO3 hết

Theo PTHH: nCO2=nCaCl2= nCaCO3= 0,1 mol

Khối lượng dung dịch sau phản ứng là: mdd= mCaCO3+ mdd HCl- mCO2= 10 + 114,1- 0,1.44=119,7 gam

→C%CaCl2=mCaCl2.100%mdd=0,1.111.100%119,7=9,27%→C%CaCl2=mCaCl2.100%mdd=0,1.111.100%119,7=9,27%

a) PT phân tử: \(CaCO_3+2HCl\rightarrow CaCl_2+H_2O+CO_2\uparrow\)

    PT ion: \(CaCO_3+2H^+\rightarrow Ca^{2+}+H_2O+CO_2\uparrow\)

b) Ta có: \(\left\{{}\begin{matrix}n_{CaCO_3}=\dfrac{10}{100}=0,1\left(mol\right)\\n_{HCl}=\dfrac{43,8\cdot20\%}{36,5}=0,24\left(mol\right)\end{matrix}\right.\)

Xét tỉ lệ: \(\dfrac{0,1}{1}< \dfrac{0,24}{2}\) \(\Rightarrow\) HCl dư, tính theo CaCO₃

\(\Rightarrow\left\{{}\begin{matrix}n_{CaCl_2}=0,1\left(mol\right)=n_{CO_2}\\n_{HCl\left(dư\right)}=0,04\left(mol\right)\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}m_{CaCl_2}=0,1\cdot111=11,1\left(g\right)\\m_{CO_2}=0,1\cdot44=4,4\left(g\right)\\m_{HCl\left(dư\right)}=0,04\cdot36,5=1,46\left(g\right)\end{matrix}\right.\)

Mặt khác: \(m_{dd}=m_{CaCO_3}+m_{ddHCl}-m_{CO_2}=49,4\left(g\right)\)

\(\Rightarrow\left\{{}\begin{matrix}C\%_{CaCl_2}=\dfrac{11,1}{49,4}\cdot100\%\approx22,47\%\\C\%_{HCl\left(dư\right)}=\dfrac{1,46}{49,4}\cdot100\%\approx2,96\%\end{matrix}\right.\)

Bổ sung: \(D_{HCl}=1,18\left(g/ml\right)\)

a) PTHH: \(MgO+2HCl\rightarrow MgCl_2+H_2O\)

b) Ta có: \(\left\{{}\begin{matrix}n_{MgO}=\dfrac{2}{40}=0,05\left(mol\right)\\n_{HCl}=\dfrac{100\cdot1,18\cdot20\%}{36,5}=\dfrac{236}{365}\left(mol\right)\end{matrix}\right.\)

Xét tỉ lệ: \(\dfrac{0,05}{1}< \dfrac{\dfrac{236}{365}}{2}\) \(\Rightarrow\) HCl còn dư, MgO p/ứ hết

\(\Rightarrow n_{MgCl_2}=0,05\left(mol\right)\) \(\Rightarrow C_{M_{MgCl_2}}=\dfrac{0,05}{0,1}=0,5\left(M\right)\)

PTHH: \(CaCO_3+2HCl\rightarrow CaCl_2+H_2O+CO_2\uparrow\)

a) Ta có: \(n_{CaCO_3}=\dfrac{2,5}{100}=0,025\left(mol\right)\)

\(\Rightarrow n_{HCl}=0,05mol\) \(\Rightarrow m_{ddHCl}=\dfrac{0,05\cdot36,5}{18\%}\approx10,14\left(g\right)\)

b) Theo PTHH: \(n_{CaCl_2}=n_{CO_2}=n_{CaCO_3}=0,025\left(mol\right)\)

\(\Rightarrow\left\{{}\begin{matrix}m_{CaCl_2}=0,025\cdot111=2,775\left(g\right)\\m_{CO_2}=0,025\cdot44=1,1\left(g\right)\end{matrix}\right.\)

Mặt khác: \(m_{dd\left(saup/ứ\right)}=m_{Zn}+m_{ddHCl}-m_{CO_2}=11,54\left(g\right)\)

\(\Rightarrow C\%_{CaCl_2}=\dfrac{2,775}{11,54}\cdot100\%\approx24,05\%\)

CaCO₃+2HCl→CaCl₂+CO₂↑ +H₂O

\(+n_{CaCO_3}=\dfrac{2,5}{100}=0,025\left(mol\right)\)

\(+n_{HCl}=2n_{CaCO_3}=0,05\left(mol\right)\)

\(+m_{HCl}=0,05.98=4,9\left(gam\right)\)

\(+m_{dungdịchHCl}=\dfrac{4,9}{18}.100\%=27,2\left(gam\right)\)

\(+n_{CaCl}=n_{CaCO_3}=0,025\left(mol\right)\)

\(+m_{CaCl_2}=0,025.111=2,775\left(gam\right)\)

Theo ĐLBTKL ta có:

\(m_{CaCl_2}=2,5+27,2-0,025.44-0,025.18=28,15\left(gam\right)\)

C%=\(\dfrac{2,775}{28,15}.100\%\approx9,85\%\)

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