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\(a.2Al+6HCl->2AlCl_3+3H_2\\ Mg+2HCl->MgCl_2+H_2\\ b.n_{Al}=a,n_{Mg}=b\\ 27a+24b=7,5\left(I\right)\\ 1,5a+b=\dfrac{7,84}{22,4}=0,35\left(II\right)\\ a=0,1;b=0,2\\ \%m_{Al}=\dfrac{27\cdot0,1}{7,5}\cdot100\%=36\%\\ \%m_{Mg}=64\%\\ c.m_{HCl}=36,5\left(0,1\cdot3+0,2\cdot2\right)=18,25g\\ d.m_{ddsau}=7,5+\dfrac{18,25}{14,6:100}-0,35\cdot2=131,8g\\ C\%\left(AlCl_3\right)=\dfrac{133,5\cdot0,1}{131,8}\cdot100\%=10,1\%\\ C\%\left(MgCl_2\right)=\dfrac{95\cdot0,2}{131,8}\cdot100\%=14,4\%\)
\(a,n_{H_2}=\dfrac{6,72}{22,4}=0,3\left(mol\right)\)
PTHH: Ba + 2H2O ---> Ba(OH)2 + H2
0,3<-------------0,3<---------0,3
=> mBa = 0,3.137 = 41,1 (g)
=> mK2O = 59,9 - 41,1 = 18,8 (g)
\(\rightarrow\left\{{}\begin{matrix}\%m_{Ba}=\dfrac{41,1}{59,9}.100\%=68,61\%\\\%m_{K_2O}=100\%-68,61\%=31,39\%\end{matrix}\right.\)
\(b,n_{K_2O}=\dfrac{18,8}{94}=0,2\left(mol\right)\)
PTHH: K2O + H2O ---> 2KOH
0,2----------------->0,4
Các chất tan trong dd sau phản ứng: KOH, Ba(OH)2
\(\rightarrow\left\{{}\begin{matrix}m_{KOH}=0,4.56=22,4\left(g\right)\\m_{Ba\left(OH\right)_2}=0,3.171=51,3\left(g\right)\end{matrix}\right.\)
PTHH: \(K+H_2O\rightarrow KOH+\dfrac{1}{2}H_2\uparrow\)
\(2KOH+CuSO_4\rightarrow K_2SO_4+Cu\left(OH\right)_2\downarrow\)
\(Cu\left(OH\right)_2\xrightarrow[]{t^o}CuO+H_2O\)
Ta có: \(n_{CuO}=\dfrac{24}{80}=0,3\left(mol\right)=n_{Cu\left(OH\right)_2}\)
\(\Rightarrow n_{KOH}=0,6\left(mol\right)=n_K\) \(\Rightarrow m_K=0,6\cdot39=23,4\left(g\right)\)
a.b.\(n_{H_2}=\dfrac{1,8.10^{23}}{6.10^{23}}=0,3mol\)
Gọi \(\left\{{}\begin{matrix}n_{Na}=x\\n_{Ba}=y\end{matrix}\right.\)
\(2Na+2H_2O\rightarrow2NaOH+H_2\)
x x 1/2 x ( mol )
\(Ba+2H_2O\rightarrow Ba\left(OH\right)_2+H_2\)
y 2y y ( mol )
Ta có:
\(\left\{{}\begin{matrix}23x+137y=22,9\\\dfrac{1}{2}x+y=0,3\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=0,4\\y=0,1\end{matrix}\right.\)
\(m_{H_2O}=\left[0,4+\left(2.0,1\right)\right].18=10,8g\)
c.\(m=22,9+10,8-0,3.2=33,1g\)
d.\(m_{Na}=0,4.23=9,2g\)
\(m_{Ba}=0,1.137=13,7g\)
PTHH: \(Mg+2HCl\rightarrow MgCl_2+H_2\uparrow\)
\(MgO+2HCl\rightarrow MgCl_2+H_2O\)
a) Ta có: \(n_{H_2}=\dfrac{11,2}{22,4}=0,5\left(mol\right)=n_{Mg}\)
\(\Rightarrow\%m_{Mg}=\dfrac{0,5\cdot24}{16}=75\%\) \(\Rightarrow\%m_{MgO}=25\%\)
b) Ta có: \(\left\{{}\begin{matrix}n_{Mg}=0,5\left(mol\right)\\n_{MgO}=\dfrac{16\cdot25\%}{40}=0,1\left(mol\right)\end{matrix}\right.\)
\(\Rightarrow n_{HCl}=2n_{Mg}+2n_{MgO}=1,2\left(mol\right)\) \(\Rightarrow m_{ddHCl}=\dfrac{1,2\cdot36,5}{20\%}=219\left(g\right)\)
c) Theo các PTHH: \(\left\{{}\begin{matrix}n_{H_2}=0,5\left(mol\right)\\n_{MgCl_2}=0,6\left(mol\right)\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}m_{H_2}=0,5\cdot2=1\left(g\right)\\m_{MgCl_2}=0,6\cdot95=57\left(g\right)\end{matrix}\right.\)
Mặt khác: \(m_{dd}=m_{hhA}+m_{ddHCl}-m_{H_2}=234\left(g\right)\) \(\Rightarrow C\%_{MgCl_2}=\dfrac{57}{234}\cdot100\%\approx24,36\%\)
Cho mình hỏi ở cái PTHH ấy! sao ta không tính số mol ở dưới??
Gọi \(\left\{{}\begin{matrix}n_{NaOH}=a\left(mol\right)\\n_{KOH}=b\left(mol\right)\end{matrix}\right.\)
\(n_{Mg\left(OH\right)_2}=\dfrac{14,5}{58}=0,25\left(mol\right)\)
PTHH:
2NaOH + MgSO4 ---> Mg(OH)2 + Na2SO4
a -----------------------------> 0,5a
2KOH + MgSO4 ---> Mg(OH)2 + K2SO4
b -------------------------------> 0,5b
Hệ pt \(\left\{{}\begin{matrix}40a+56b=24,8\\0,5a+0,5b=0,25\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}a=0,2\left(mol\right)\\b=0,3\left(mol\right)\end{matrix}\right.\)
\(\rightarrow\left\{{}\begin{matrix}m_{NaOH}=0,2.40=8\left(g\right)\\m_{KOH}=0,3.56=16,8\left(g\right)\end{matrix}\right.\rightarrow\left\{{}\begin{matrix}\%m_{NaOH}=\dfrac{8}{24,8}=32,26\%\\\%m_{KOH}=100\%-32,26\%=67,74\%\end{matrix}\right.\)
2NaOH+MgSO4->Mg(OH)2+Na2SO4
x-----------------------------1\2x
2KOH+MgSO4->K2SO4+Mg(OH)2
y--------------------------------------1\2y
=> ta có :
\(\left\{{}\begin{matrix}40x+56y=24,8\\0,5x+0,5y=0,25\end{matrix}\right.=>\left\{{}\begin{matrix}x=0,2\\y=0,3\end{matrix}\right.\)
%mNaOH=\(\dfrac{0,2.40}{24,8}100\)=32,25%
=>%m KOH=67,75%