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Bài 3.
\(n_{Fe}=\dfrac{m_{Fe}}{M_{Fe}}=\dfrac{36}{56}=0,6428mol\)
\(3Fe+2O_2\rightarrow\left(t^o\right)Fe_3O_4\)
0,6428 ----- 0,4285 ( mol )
\(2KMnO_4\rightarrow\left(t^o\right)K_2MnO_4+MnO_2+O_2\)
0,857 0,4285 ( mol )
\(m_{KMnO_4}=n_{KMnO_4}.M_{KMnO_4}=0,857.158=135,406g\)
Bài 4.
a.\(n_{Al_2O_3}=\dfrac{m_{Al_2O_3}}{M_{Al_2O_3}}=\dfrac{51}{102}=0,5mol\)
\(4Al+3O_2\rightarrow\left(t^o\right)2Al_2O_3\)
1 0,75 0,5 ( mol )
\(m_{Al}=n_{Al}.M_{Al}=1.27=27g\)
\(V_{O_2}=n_{O_2}.22,4=0,75.22,4=16,8l\)
b.\(2KMnO_4\rightarrow\left(t^o\right)K_2MnO_4+MnO_2+O_2\)
1,5 0,75 ( mol )
\(m_{KMnO_4}=n_{KMnO_4}.M_{KMnO_4}=1,5.158=237g\)
\(2KClO_3\rightarrow\left(t^o\right)2KCl+3O_2\)
0,5 0,75 ( mol )
\(m_{KClO_3}=n_{KClO_3}.M_{KClO_3}=0,5.122,5=61,25g\)
\(n_{Al}=\dfrac{5,4}{54}=0,1(mol)\\ 4Al+3O_2\xrightarrow{t^o}2Al_2O_3\\ \Rightarrow n_{O_2}=\dfrac{3}{4}n_{Al}=0,075(mol);n_{Al_2O_3}=\dfrac{1}{2}n_{Al}=0,05(mol)\\ \Rightarrow V_{O_2}=0,075.22,4=1,68(l);m_{Al_2O_3}=0,05.102=5,1(g)\)
a: \(2Al+6HCl\rightarrow2AlCl_3+3H_2\)
\(n_{Al}=\dfrac{5.4}{27}=0.2\left(mol\right)\)
\(n_{HCl}=\dfrac{10.95}{36.5}=0.3\left(mol\right)\)
Vì \(\dfrac{0.2}{2}>\dfrac{0.3}{6}\) nên Al dư và dư 0,05 mol
b: \(n_{AlCl_3}=0.9\left(mol\right)\)
\(m_{AlCl_3}=0.9\cdot136.5=122.85\left(g\right)\)
a, PT: \(4Al+3O_2\underrightarrow{t^o}2Al_2O_3\)
b, Ta có: \(n_{Al}=\dfrac{5,4}{27}=0,2\left(mol\right)\)
Theo PT: \(n_{O_2}=\dfrac{3}{4}n_{Al}=0,15\left(mol\right)\)
\(\Rightarrow V_{O_2}=0,15.22,4=3,36\left(l\right)\)
c, Theo PT: \(n_{Al_2O_3}=\dfrac{1}{2}n_{Al}=0,1\left(mol\right)\)
\(\Rightarrow m_{Al_2O_3}=0,1.102=10,2\left(g\right)\)
a) \(4Al + 3O_2 \xrightarrow{t^o} 2Al_2O_3\)
b)
\(n_{Al} = \dfrac{21,6}{27} = 0,8(mol)\)
Theo PTHH :
\(n_{Al_2O_3} = \dfrac{1}{2}n_{Al} = 0,4(mol)\\ \Rightarrow m_{Al_2O_3} = 0,4.102 = 40,8(gam)\)
c)
\(n_{O_2} = \dfrac{3}{4}n_{Al} = 0,6(mol)\\ \Rightarrow V_{O_2} = 0,6.22,4 = 13,44(lít)\\ \Rightarrow V_{không\ khí} = 5V_{O_2} = 13,44.5 = 67,2(lít)\)
Bảo toàn KL: \(m_{Al_2O_3}=m_{Al}+m_{O_2}=15+14=29(g)\)