a,\(n_{CuO}=\dfrac{20}{80}=0,25\left(mol\right)\)

PTHH: CuO + H₂SO₄ →CuSO₄ + H₂O

Mol:     0,25      0,25         0,25

\(m_{ddH_2SO_4}=\dfrac{0,25.98.100}{19,6}=125\left(g\right)\)

b,m_{dd sau pứ} = 20+125 = 145 (g)

\(C\%_{ddCuSO_4}=\dfrac{0,25.160.100\%}{145}=27,59\%\)

\(Cu+H_2SO_4\rightarrow CuSO_4+H_2\)
0,3125    0,3125   0,3125        (mol)
a)\(n_{Cu}=\dfrac{20}{64}=0,3125\left(mol\right)\)
\(m_{H_2SO_4}=0,3125.98=30,625\left(g\right)\)
\(m_{ddH_2SO_4}=\dfrac{30,625}{19,6}.100=156,25\left(g\right)\)
b)\(m_{CuSO_4}=0,3125.160=50\left(g\right)\)
\(m_{ddCuSO_4}=20+156,25=176,25\left(g\right)\)
\(C\%_{CuSO_4}=\dfrac{50}{176,25}.100\approx28,37\%\)

\(n_{CuO}=\dfrac{20}{80}=0,25\left(mol\right)\\ CuO+H_2SO_4\rightarrow CuSO_4+H_2O\\ a.0,25.........0,25..........0,25.......0,25\left(mol\right)\\ Đặt:a=m_{ddH_2SO_4}\left(g\right)\Rightarrow m_{ddX}=a+20\left(g\right)\\Vì.axit.dư\Rightarrow m_{CuSO_4}=0,25.160=40\left(g\right)\\ \dfrac{40}{a+20}.100\%=16\%\Leftrightarrow a=230\left(g\right)\\ \Rightarrow m_{ddH_2SO_4}=230\left(g\right)\\ b.m_{H_2SO_4\left(dư\right)}=230.19,6\%-0,25.98=20,58\left(g\right)\\ C\%_{ddH_2SO_4\left(dư\right)}=\dfrac{20,58}{230+20}.100=8,232\%\)

Oxit kim loại : R₂O_n

\(\%R = \dfrac{2R}{2R + 16n}.100\% = 60\%\\ \Rightarrow R = 12n\)

Với n = 2 thì R = 24(Magie)

Vậy oxit là MgO

\(MgO+ H_2SO_4 \to MgSO_4 + H_2O\\ n_{MgSO_4} = n_{H_2SO_4} = n_{MgO} = \dfrac{20}{40} = 0,5(mol)\\ \Rightarrow m_{dd\ H_2SO_4} =\dfrac{0,5.98}{10\%} = 490(gam)\\ m_{dd\ sau\ pư} = 20 + 490 = 510(gam)\\ \Rightarrow C\%_{MgSO_4} = \dfrac{0,5.120}{510}.100\% = 11,76\%\)

\(n_{Fe2O3}=\dfrac{24}{160}=0,15\left(mol\right)\)

\(m_{ct}=\dfrac{19,6.300}{100}=58,8\left(g\right)\)

\(n_{H2SO4}=\dfrac{58,8}{98}=0,6\left(mol\right)\)

Pt : \(Fe_2O_3+3H_2SO_4\rightarrow Fe_2\left(SO_4\right)_3+3H_2|\)

           1              3                     1              3

          0,15        0,6                  0,15

a) Lập tỉ số so sánh : \(\dfrac{0,15}{1}< \dfrac{0,6}{3}\)

                ⇒ Fe₂O₃ phản ứng hết , H₂SO₄ dư

                 ⇒ Tính toán dựa vào số mol của Fe₂O₃

\(n_{Fe2\left(SO4\right)3}=\dfrac{0,15.1}{1}=0,15\left(mol\right)\)

⇒ \(m_{Fe2\left(SO4\right)3}=0,15.400=60\left(g\right)\)

b) Dung dịch X sau phản ứng gồm : \(Fe_2\left(SO_4\right)_3\) va dung dịch \(H_2SO_4\) dư

\(n_{H2SO4\left(dư\right)}=0,6-\left(0,15.3\right)=0,15\left(mol\right)\)

⇒ \(m_{H2SO4\left(dư\right)}=0,15.98=14,7\left(g\right)\)

\(m_{ddspu}=24+300-324\left(g\right)\)

\(C_{Fe2\left(SO4\right)3}=\dfrac{60.100}{324}=18,52\)⁰/₀

\(C_{H2SO4\left(dư\right)}=\dfrac{14,7.100}{324}=4,54\)⁰/₀

 Chúc bạn học tốt

Cái này bắt tính %m dd sau pư nên cần tính m dung dịch sau pư
ta có m_{dung dịch(sau pư)}= m_{chất tan}+ m_{dung môi} - m_{khí và rắn nếu có}

a) Gọi \(\left\{{}\begin{matrix}n_{Mg}=a\left(mol\right)\\n_{Fe}=b\left(mol\right)\end{matrix}\right.\)

PTHH: Mg + H₂SO₄ --> MgSO₄ + H₂

             a--->a---------->a-------->a

            Fe + H₂SO₄ --> FeSO₄ + H₂

             b--->b----------->b------>b

=> \(m_{H_2SO_4}=98a+98b\left(g\right)\)

=> \(m_{ddH_2SO_4}=\dfrac{\left(98a+98b\right).100}{19,6}=500a+500b\left(g\right)\)

m_{dd sau pư} = 24a + 56b + 500a + 500b - 2a - 2b = 522a + 554b (g)

Có: \(C\%_{FeSO_4}=\dfrac{152b}{522a+554b}.100\%=7,17\%\)

=> a = 3b

\(C\%_{MgSO_4}=\dfrac{120a}{522a+554b}.100\%=16,98\%\)

b)

Có: \(\left\{{}\begin{matrix}a=3b\\24a+56b=1,92\end{matrix}\right.\)

=> a = 0,045; b = 0,015

\(n_{CuSO_4}=0,1.1=0,1\left(mol\right)\)

PTHH: Mg + CuSO₄ --> MgSO₄ + Cu

         0,045->0,045----->0,045

            Fe + CuSO₄ --> FeSO₄ + Cu

       0,015-->0,015----->0,015

=> \(\left\{{}\begin{matrix}n_{CuSO_4\left(dư\right)}=0,04\left(mol\right)\\n_{MgSO_4}=0,045\left(mol\right)\\n_{FeSO_4}=0,015\left(mol\right)\end{matrix}\right.\)

=> \(\left\{{}\begin{matrix}C_{M\left(CuSO_4\left(dư\right)\right)}=\dfrac{0,04}{0,1}=0,4M\\C_{M\left(MgSO_4\right)}=\dfrac{0,045}{0,1}=0,45M\\C_{M\left(FeSO_4\right)}=\dfrac{0,015}{0,1}=0,15M\end{matrix}\right.\)

\(\left(a\right)Zn+2HCl\rightarrow ZnCl_2+H_2\\ DungdịchX:ZnCl_2, A:H_2,B:Ag\\ n_{H_2}=\dfrac{5,6}{22,4}=0,25\left(mol\right)\\ n_{HCl}=2n_{H_2}=0,5\left(mol\right)\\ \Rightarrow x=m_{ddHCl}=\dfrac{0,5.36,5}{3,65}=500\left(g\right)\\ n_{Zn}=n_{H_2}=0,2\left(mol\right)\\ \Rightarrow y=m_{Ag}=27,05-0,2.65=14,05\left(g\right)\\ \left(b\right):m_{ddsaupu}=0,2.65+500-0,2.2=512,6\left(g\right)\\ TheoPT:n_{ZnCl_2}=n_{H_2}=0,2\left(mol\right)\\ C\%_{ZnCl_2}=\dfrac{0,2.136}{512,5}.100=5,3\%\)