\(n_{Fe}=\dfrac{5,6}{56}=0,1\left(mol\right)\\ PTHH:Fe+2HCl\rightarrow FeCl_2+H_2\\ n_{FeCl_2}=n_{H_2}=n_{Fe}=0,1\left(mol\right)\\ m_{ddFeCl_2}=5,6+50-0,1.2=55,4\left(g\right)\\ C\%_{ddFeCl_2}=\dfrac{127.0,1}{55,4}.100\%\approx22,924\%\)

1. Gọi CTHH của oxit là N_xO_y.

Ta có: \(\dfrac{m_N}{m_O}=\dfrac{7}{20}\Rightarrow\dfrac{n_N}{n_O}=\dfrac{7}{20}:\dfrac{14}{16}=\dfrac{2}{5}\)

⇒ x:y = 2:5

→ N₂O₅

2. Gọi CTHH cần tìm là Fe_xO_y.

\(\Rightarrow\dfrac{m_{Fe}}{m_O}=\dfrac{7}{2}\Rightarrow\dfrac{n_{Fe}}{n_O}=\dfrac{7}{2}:\dfrac{56}{16}=1\)

⇒ x:y = 1

→ FeO

3. CTHH cần tìm: RO₂

Mà: %R = 46,7%
\(\Rightarrow\dfrac{M_R}{M_R+16.2}.100\%=46,7\%\)

⇒ M_R = 28 (g/mol)

→ SiO₂

Nồng độ %? hoặc 500 ml dd HCl

\(n_{CaCO_3}=\dfrac{30}{100}=0,3mol\\ CaCO_3+2HCl\rightarrow CaCl_2+CO_2+H_2O\\ n_{HCl}=0,3.2=0,6mol\\ \left[{}\begin{matrix}C_{M_{HCl}}\\C_{\%HCl}=\dfrac{0,6.36,5}{500}\cdot100=4,38\%\end{matrix}\right.=\dfrac{0,6}{0,5}=1,2M}\)

\(SO_3+H_2O\rightarrow H_2SO_4\\ H_2SO_4+Na_2SO_3\rightarrow Na_2SO_4+SO_2+H_2O\\ SO_2+Na_2O\rightarrow Na_2SO_3\\ Na_2SO_3+2HCl\rightarrow2NaCl+SO_2+H_2O\)

1, SO₃+H₂O->H₂SO₄

2, H₂SO₄+Na₂SO₃->Na₂SO₄+H₂O+SO₂

3, SO₂+2NaOH->Na₂SO₃+H₂O

4, Na₂SO₃+H₂SO₄->Na₂SO₄+H₂O+SO₂

a, \(Al_2O_3+6HCl\rightarrow2AlCl_3+3H_2O\)

Ta có: \(n_{Al_2O_3}=\dfrac{15,3}{102}=0,15\left(mol\right)\)

b, \(n_{AlCl_3}=2n_{Al_2O_3}=0,3\left(mol\right)\Rightarrow m_{AlCl_3}=0,3.133,5=40,05\left(g\right)\)

c, \(n_{HCl}=6n_{Al_2O_3}=0,9\left(mol\right)\Rightarrow m_{ddHCl}=\dfrac{0,9.36,5}{14,6\%}=225\left(g\right)\)

d, m _{dd sau pư} = 15,3 + 225 = 240,3 (g)

\(\Rightarrow C\%_{AlCl_3}=\dfrac{40,05}{240,3}.100\%\approx16,67\%\)

e, n_H2SO4 = 0,3.1 = 0,3 (mol)

PT: \(Al_2O_3+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2O\)

Xét tỉ lệ: \(\dfrac{0,15}{1}>\dfrac{0,3}{3}\), ta được Al₂O₃ dư.

→ Al₂O₃ không tan hết.