Câu 2:

a, \(n_{Fe_2O_3}=\dfrac{6,4}{160}=0,04\left(mol\right)\)

\(n_{H_2SO_4}=0,5.1=0,5\left(mol\right)\)

PT: \(Fe_2O_3+3H_2SO_4\rightarrow Fe_2\left(SO_4\right)_3+3H_2O\)

Xét tỉ lệ: \(\dfrac{0,04}{1}< \dfrac{0,5}{3}\), ta được H₂SO₄ dư.

Vậy: Fe₂O₃ tan hết.

b, Theo PT: \(\left\{{}\begin{matrix}n_{Fe_2\left(SO_4\right)_3}=n_{Fe_2O_3}=0,04\left(mol\right)\\n_{H_2SO_4\left(pư\right)}=3n_{Fe_2O_3}=0,12\left(mol\right)\end{matrix}\right.\)

\(\Rightarrow n_{H_2SO_4\left(dư\right)}=0,5-0,12=0,38\left(mol\right)\)

\(\Rightarrow\left\{{}\begin{matrix}C_{M_{Fe_2\left(SO_4\right)_3}}=\dfrac{0,04}{0,5}=0,08\left(M\right)\\C_{M_{H_2SO_4\left(dư\right)}}=\dfrac{0,38}{0,5}=0,76\left(M\right)\end{matrix}\right.\)

Câu 3:

a, \(n_{Ba\left(OH\right)_2}=0,2.1=0,2\left(mol\right)\)

\(n_{H_2SO_4}=0,3.0,72=0,216\left(mol\right)\)

PT: \(Ba\left(OH\right)_2+H_2SO_4\rightarrow BaSO_{4\downarrow}+2H_2O\)

Xét tỉ lệ: \(\dfrac{0,2}{1}< \dfrac{0,216}{1}\), ta được H₂SO₄ dư.

Theo PT: \(n_{BaSO_4}=n_{Ba\left(OH\right)_2}=0,2\left(mol\right)\Rightarrow m_{BaSO_4}=0,2.233=46,6\left(g\right)\)

b, Theo PT: \(n_{H_2SO_4\left(pư\right)}=n_{Ba\left(OH\right)_2}=0,2\left(mol\right)\Rightarrow n_{H_2SO_4\left(dư\right)}=0,216-0,2=0,016\left(mol\right)\)

\(\Rightarrow C_{M_{H_2SO_4\left(dư\right)}}=\dfrac{0,016}{0,2+0,3}=0,032\left(M\right)\)

c, - Nhúng quỳ tím vào dd thấy quỳ hóa đỏ do H₂SO₄ dư.

\(n_{CuO}=\dfrac{8}{80}=0.1\left(mol\right)\)

\(CuO+H_2SO_4\rightarrow CuSO_4+H_2O\)

\(0.1...........0.1.........0.1\)

\(n_{NaOH}=0.24\cdot0.5=0.12\left(mol\right)\)

\(2NaOH+H_2SO_4\rightarrow Na_2SO_4+H_2O\)

\(0.12..........0.06\)

\(n_{H_2SO_4}=0.1+0.06=0.16\left(mol\right)\)

\(V_{dd_{H_2SO_4}}=\dfrac{0.16}{1}=0.16\left(l\right)\)

\(C_{M_{H_2SO_4\left(dư\right)}}=\dfrac{0.06}{0.16}=0.375\left(M\right)\)

\(C_{M_{CuSO_4}}=\dfrac{0.1}{0.16}=0.625\left(M\right)\)

PTHH: \(Mg+2HCl\rightarrow MgCl_2+H_2\uparrow\)

            \(2Al+6HCl\rightarrow2AlCl_3+3H_2\uparrow\)

            \(Fe+2HCl\rightarrow FeCl_2+H_2\uparrow\)

a) Ta có: \(\left\{{}\begin{matrix}n_{HCl}=\dfrac{12,7}{36,5}=\dfrac{127}{365}\left(mol\right)\\n_{H_2}=\dfrac{3,36}{22,4}=0,15\left(mol\right)\end{matrix}\right.\)

Ta thấy: \(2n_{H_2}< n_{HCl}\) \(\Rightarrow\) Axit còn dư

b) Theo PTHH: \(n_{HCl\left(p/ứ\right)}=2n_{H_2}=0,3\left(mol\right)\) \(\Rightarrow m_{HCl}=0,3\cdot36,5=10,95\left(g\right)\)

Mặt khác: \(m_{H_2}=0,15\cdot2=0,3\left(g\right)\)

Bảo toàn khối lượng: \(m_{muối}=m_{KL}+m_{HCl\left(p/ứ\right)}-m_{H_2}=18,65\left(g\right)\)

Đáp án D.

Đáp án D

Đáp án D.