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\(n_{Fe_2O_3}=\dfrac{16}{160}=0,1\left(mol\right)\)
PTHH: Fe2O3 + 3H2 --to--> 2Fe + 3H2O
0,1---->0,3
Zn + H2SO4 --> ZnSO4 + H2
0,3<--------------------0,3
=> m = 0,3.65 = 19,5 (g)
a)
$R + 2HCl \to RCl_2 + H_2$
$Zn + 2HCl \to ZnCl_2 + H_2$
b)$n_{H_2} = \dfrac{6,72}{22,4} = 0,3(mol)$
Gọi $n_R = a(mol) \Rightarrow n_{Zn} = 2a(mol)$
$\Rightarrow a + 2a = 0,3 \Rightarrow a = 0,1$
$\RIghtarrow 0,1.R + 0,2.65 = 18,6$
$\Rightarrow R = 56(Fe)$
$n_{FeCl_2} = n_{Fe} = 0,1(mol) ; n_{ZnCl_2} = n_{Zn} = 0,2(mol)$
$m_{FeCl_2} = 0,1.127 = 12,7(gam)$
$n_{ZnCl_2} = 0,2.161 =32,2(gam)$
$n_{HCl} = 2n_{H_2} = 0,3(mol) \Rightarrow V_{dd\ HCl} = \dfrac{0,3}{1,5} = 0,2(lít)$
c) Kim loại R là Fe
a, PT: \(R+H_2SO_4\rightarrow RSO_4+H_2\)
\(2Al+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2\)
b, Ta có: \(n_{H_2}=\dfrac{8,96}{22,4}=0,4\left(mol\right)\)
Theo PT: \(n_{H_2SO_4}=n_{H_2}=0,4\left(mol\right)\)
\(\Rightarrow V_{ddH_2SO_4}=\dfrac{0,4}{2}=0,2\left(l\right)\)
Theo ĐLBT KL, có: mKL + mH2SO4 = m muối + mH2
⇒ m muối = 7,8 + 0,4.98 - 0,4.2 = 46,2 (g)
c, Gọi: nR = x (mol) → nAl = 2x (mol)
Theo PT: \(n_{H_2}=n_R+\dfrac{3}{2}n_{Al}=x+\dfrac{3}{2}.2x=0,4\left(mol\right)\Rightarrow x=0,1\left(mol\right)\)
⇒ nR = 0,1 (mol)
nAl = 0,1.2 = 0,2 (mol)
⇒ 0,1.MR + 0,2.27 = 7,8 ⇒ MR = 24 (g/mol)
Vậy: R là Mg.
Tính được : \(n_{H2}=0,1\left(mol\right)\)
PTHH :
\(R+H_2SO_4\rightarrow RSO_4+H_2\)
\(1..1...........1........1\)
\(0,1......0,1..........0,1.........0,1\)
\(M_R=\frac{M_R}{M_R}=\frac{2,5}{0,1}=25\) ( g/mol )
Vậy \(R=25\)
Nếu A không có K:
\(\%m_K=\dfrac{10,66}{29,34+10,66}\cdot100\%=26,65\%\ne29,35\%\\ R:Kali\\ K+H_2O->KOH+\dfrac{1}{2}H_2\\ M+2H_2O->M\left(OH\right)_2+H_2\\ n_K=a,n_M=b\left(mol\right)\\ n_{H_2}=0,5a+b=\dfrac{5,376}{22,4}=0,24mol\\ \%m_{K\left(B\right)}=\dfrac{39a+10,66}{29,34+10,66}\cdot100=29,35\\ a=0,028\\ b=0,226\\ M_M=\dfrac{29,34-39\cdot0,028}{0,226}=125\left(g\cdot mol^{^{-1}}\right)\)
Vậy không có kim loại kiềm thổ thoả đề
\(R+2H_2O->R\left(OH\right)_2+H_2\\ n_R=n_{ROH}\\ \Rightarrow16,44:M_R=\dfrac{20,52}{M_R+17\cdot2}\\ M_R=137\left(Ba:barium\right)\)
\(n_R=\dfrac{16,44}{R}\left(mol\right);n_{R\left(OH\right)_2}=\dfrac{20,52}{R+\left(1+16\right).2}=\dfrac{20,52}{R+34}\left(mol\right)\\ R+H_2O\xrightarrow[]{}R\left(OH\right)_2+H_2\\ \Rightarrow n_R=n_{R\left(OH\right)_2}\\ \Leftrightarrow\dfrac{16,44}{R}=\dfrac{20,52}{R+34}\\ \Leftrightarrow16,44.\left(R+34\right)=R.20,52\\ \Leftrightarrow16,44R+558,96=20,52R \\ \Leftrightarrow558,96=20,52R-16,44R\\ \Leftrightarrow558,96=4,08R\\ \Leftrightarrow R=137\\\)
⇒R là Ba(Bari, 137)
\(R+H_2SO_4\rightarrow RSO_4+H_2\\ n_{H_2}=\dfrac{7,168}{22,4}=0,32\left(mol\right)\\ n_R=n_{H_2}=0,32\left(mol\right)\\ M_R=\dfrac{7,68}{0,32}=24\left(\dfrac{g}{mol}\right)\\ \Rightarrow R\left(II\right):Magie\left(Mg=24\right)\)
C
\(n_{H_2}=\dfrac{5.376}{22,4}=0,24\left(mol\right)\)
PTHH : R + H2SO4 -> RSO4 + H2
0,24 0,24
\(M_R=\dfrac{9.6}{0,24}=40\left(\dfrac{g}{mol}\right)\)
Chọn C