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a) Gọi số mol Mg, Al, Fe trong m gam hỗn hợp là a, b, c (mol)
\(n_{H_2}=\dfrac{7,84}{22,4}=0,35\left(mol\right)\)
PTHH: \(Mg+2HCl\rightarrow MgCl_2+H_2\uparrow\)
_______a--------------------->a------->a_______(mol)
\(2Al+6HCl\rightarrow2AlCl_3+3H_2\uparrow\)
_b-------------------->b------->1,5b___________(mol)
\(Fe+2HCl\rightarrow FeCl_2+H_2\uparrow\)
_c------------------>c------->c_______________(mol)
=> \(\left\{{}\begin{matrix}a+1,5b+c=0,35\left(1\right)\\95a+133,5b+127c=35,55\left(2\right)\end{matrix}\right.\)
Mặt khác:
PTHH: \(Mg+Cl_2\underrightarrow{t^o}MgCl_2\)
_______a--------------->a_________(mol)
\(2Al+3Cl_2\underrightarrow{t^o}2AlCl_3\)
_b----------------->b______________(mol)
\(2Fe+3Cl_2\underrightarrow{t^o}2FeCl_3\)
_c------------------>c______________(mol)
=> 95a + 133,5b + 162,5 = 39,1 (3)
(1)(2)(3) => \(\left\{{}\begin{matrix}a=0,1\left(mol\right)\\b=0,1\left(mol\right)\\c=0,1\left(mol\right)\end{matrix}\right.\)
=> m = 24.0,1 + 27.01 + 56.0,1 = 10,7(g)
b) \(\left\{{}\begin{matrix}m_{Mg}=24.0,1=2,4\left(g\right)\\m_{Al}=27.0,1=2,7\left(g\right)\\m_{Fe}=56.0,1=5,6\left(g\right)\end{matrix}\right.\)
Đặt \(\left\{{}\begin{matrix}n_{CaCO_3}=x\\n_{MgCO_3}=y\end{matrix}\right.\) ( mol )
\(\Rightarrow m_{hh}=100x+84y=14,2\left(g\right)\) (1)
\(CaCO_3\rightarrow\left(t^o\right)CaO+CO_2\)
x x x ( mol )
\(MgCO_3\rightarrow\left(t^o\right)MgO+CO_2\)
y y y ( mol )
\(Ca\left(OH\right)_2+CO_2\rightarrow CaCO_3\downarrow+H_2O\)
0,15 0,15 ( mol )
\(n_{CaCO_3}=\dfrac{15}{100}=0,15\left(mol\right)\)
\(\Rightarrow n_{CO_2}=x+y=0,15\left(mol\right)\) (2)
\(\left(1\right);\left(2\right)\Rightarrow\left\{{}\begin{matrix}x=0,1\\y=0,05\end{matrix}\right.\)
\(\left\{{}\begin{matrix}\%m_{CaCO_3}=\dfrac{0,1.100}{14,2}.100=70,42\%\\\%m_{MgCO_3}=100-70,42=29,58\%\end{matrix}\right.\)
\(m_{rắn}=m_{CaO}+m_{MgO}=0,1.56+0,05.40=7,6\left(g\right)\)
\(V_{CO_2}=0,15.22,4=3,36\left(l\right)\)
Zn + 2HCl → ZnCl2 + H2
số mol H2 :
nH2 = 0,224 / 22,4 = 0,01(mol)
theo phương trình trình hóa học ta có :
nZn = nH2= 0,01 (mol)
nHCl = 2nH2 = 0,02 (mol)
=> mZn = 0,01. 65 = 0,65 (g)
=> VHCl = 0.02/0,2= 0,1 (l)
\(n_{CO_2}=\dfrac{5,6}{22,4}=0,25\left(mol\right)\)
PT: \(CO_2+Ca\left(OH\right)_2\rightarrow CaCO_3+H_2O\)
Theo PT: \(n_{Ca\left(OH\right)_2}=n_{CaCO_3}=n_{CO_2}=0,25\left(mol\right)\)
a, \(C_{M_{Ca\left(OH\right)_2}}=\dfrac{0,25}{0,1}=2,5\left(M\right)\)
b, \(m_{CaCO_3}=0,25.100=25\left(g\right)\)
c, \(Ca\left(OH\right)_2+2HCl\rightarrow CaCl_2+2H_2O\)
Theo PT: \(n_{HCl}=2n_{Ca\left(OH\right)_2}=0,5\left(mol\right)\)
\(\Rightarrow m_{ddHCl}=\dfrac{0,5.36,5}{20\%}=91,25\left(g\right)\)
Hỗn hợp muối có Al(NO3)3 , Mg(NO3)2 , NH4NO3
nHNO3=0,87 => nNH4NO3=0,087 mol .
Đặt nAl=x , nMg=y => hệ : 27x + 24y=6,48g
3x + 2y = 0,087 .8
=> x= 0,208 , y=0,036
=> m= 56,592g
Hỗn hợp muối có Al(NO3)3 , Mg(NO3)2 , NH4NO3
nHNO3=0,87 => nNH4NO3=0,087 mol .
Đặt nAl=x , nMg=y => hệ : 27x + 24y=6,48g
3x + 2y = 0,087 .8
=> x= 0,208 , y=0,036
=> m= 56,592g
PT: \(CaCO_3+2HCl\rightarrow CaCl_2+CO_2+H_2O\) (1)
\(MgCO_3+2HCl\rightarrow MgCl_2+CO_2+H_2O\) (2)
\(Mg\left(OH\right)_2+2HCl\rightarrow MgCl_2+2H_2O\) (3)
\(K_2CO_3+2HCl\rightarrow2KCl+CO_2+H_2O\) (4)
Ta có: \(m_{HCl}=10.95.20\%=2,19\left(g\right)\Rightarrow n_{HCl}=\dfrac{2,19}{36,5}=0,06\left(mol\right)\)
\(n_{CO_2}=\dfrac{0,224}{22,4}=0,01\left(mol\right)\)
Theo PT: \(n_{HCl\left(1\right)+\left(2\right)+\left(4\right)}=2n_{CO_2}=0,02\left(mol\right)\)
\(n_{H_2O\left(1\right)+\left(2\right)+\left(4\right)}=n_{CO_2}=0,01\left(mol\right)\)
\(\Rightarrow n_{HCl\left(3\right)}=0,06-0,02=0,04\left(mol\right)=n_{H_2O\left(3\right)}\)
⇒ nH2O = 0,01 + 0,04 = 0,05 (mol)
Theo ĐLBT KL, có: mhh + mHCl = m muối + mCO2 + mH2O
⇒ m = m muối = 2,24 + 2,19 - 0,01.44 - 0,05.18 = 3,09 (g)