\(n_{P_2O_5}=\dfrac{99,4}{142}=0,7\left(mol\right)\)

\(P_2O_5+3H_2O\rightarrow2H_3PO_4\)

0,7        2,1           1,4 

a, \(m_{H_3PO_4}=1,4.98=137,2\left(g\right)\)

\(m_{ddH_3PO_4}=99,4+500=599,4\left(g\right)\)

Kl nước trong dd A :

\(m_{H_2O}=599,4-137,2=462,2\left(g\right)\)

\(b,C\%_{H_3PO_4}=\dfrac{137,2}{599,4}.100\%\approx22,89\%\)

\(c,C_M=\dfrac{n}{V}=\dfrac{1,4}{0,5}=2,8M\)

\(n_{CuO}=\dfrac{12}{80}=0,15\left(mol\right)\)

\(n_{HCl}=0,4.1=0,4\left(mol\right)\)

\(CuO+2HCl\rightarrow CuCl_2+H_2O\)

0,15 ---> 0,3 -----> 0,15 ----> 0,15

Xét: \(\dfrac{0,15}{1}< \dfrac{0,4}{2}\) => axit dư

a. HCl dư sau phản ứng và \(n_{HCl.dư}=0,4-0,3=0,1\left(mol\right)\)

b.

Trong dung dịch A có:

\(m_{HCl}=0,1.36,5=3,65\left(g\right)\)

\(m_{CuCl_2}=0,15.135=20,25\left(g\right)\\ m_{H_2O}=0,15.18=2,7\left(g\right)\)

HCl mấy M v bạn ?

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a) \(n_{SO_3}=\dfrac{3,2}{80}=0,04\left(mol\right)\)

PTHH: SO₃ + H₂O --> H₂SO₄

          0,04------------->0,04

=> \(m_{H_2SO_4}=0,04.98=3,92\left(g\right)\)

b) \(n_{Na}=\dfrac{0,69}{23}=0,03\left(mol\right)\)

PTHH: 2Na + 2H₂O --> 2NaOH + H₂

            0,03------------>0,03

           2NaOH + H₂SO₄ --> Na₂SO₄ + 2H₂O

Xét tỉ lệ: \(\dfrac{0,03}{2}< \dfrac{0,04}{1}\)=> NaOH hết, H₂SO₄ dư

2NaOH + H₂SO₄ --> Na₂SO₄ + 2H₂O

0,03------>0,015---->0,015

\(\left\{{}\begin{matrix}n_{Na_2SO_4}=0,015\left(mol\right)\\n_{H_2SO_4\left(dư\right)}=0,025\left(mol\right)\end{matrix}\right.\)

=> \(\left\{{}\begin{matrix}m_{Na_2SO_4}=0,015.142=2,13\left(g\right)\\m_{H_2SO_4}=0,025.98=2,45\left(g\right)\end{matrix}\right.\)

c) \(n_{Na}=\dfrac{2,07}{23}=0,09\left(mol\right)\)

PTHH: 2Na + 2H₂O --> 2NaOH + H₂

          0,09-------------->0,09

Xét tỉ lệ: \(\dfrac{0,09}{2}>\dfrac{0,04}{1}\) => NaOH dư, H₂SO₄ hết

2NaOH + H₂SO₄ --> Na₂SO₄ + 2H₂O

0,08<-----0,04------>0,04

=> \(\left\{{}\begin{matrix}n_{NaOH\left(dư\right)}=0,01\left(mol\right)\\n_{Na_2SO_4}=0,04\left(mol\right)\end{matrix}\right.\)

=> \(\left\{{}\begin{matrix}m_{NaOH\left(dư\right)}=0,01.40=0,4\left(g\right)\\m_{Na_2SO_4}=0,04.142=5,68\left(g\right)\end{matrix}\right.\)

Đáp án C

Chọn đáp án C

a, \(2Na+2H_2O\rightarrow2NaOH+H_2\)

\(Na_2O+H_2O\rightarrow2NaOH\)

b, Dung dịch Y chứa NaOH.

- Cách nhận biết: Nhỏ vài giọt dd vào quỳ tím thấy quỳ chuyển xanh.

c, Ta có: \(n_{H_2}=\dfrac{2,24}{22,4}=0,1\left(mol\right)\)

Theo PT: \(n_{Na}=2n_{H_2}=0,2\left(mol\right)\)

\(\Rightarrow\left\{{}\begin{matrix}\%m_{Na}=\dfrac{0,2.23}{10,8}.100\%\approx42,59\%\\\%m_{Na_2O}\approx57,41\%\end{matrix}\right.\)

Chọn C

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

\(n_{HCl}=\dfrac{14,6}{36,5}=0,4mol\)

\(n_{H_2}=\dfrac{2,24}{22,4}=0,1mol\)

a)Theo pt: \(n_{Fe}=n_{H_2}=0,1mol\)

\(\Rightarrow m_{Fe}=0,1\cdot56=5,6g\)

\(\%m_{Fe}=\dfrac{5,6}{12}\cdot100\%=46,67\%\)

\(\%m_{Cu}=100\%-46,67\%=53,33\%\)

c)\(m_{Cu}=12-5,6=6,4g\Rightarrow n_{Cu}=0,1mol\)

\(BTe:n_{O_2}=n_{Fe}+n_{Cu}=0,2mol\)

\(H=80\%\Rightarrow n_{O_2}=80\%\cdot0,2=0,16mol\)

\(n_{KMnO_4}=\dfrac{1}{2}n_{O_2}=0,08mol\)

\(\Rightarrow m_{KMnO_4}=0,08\cdot158=12,64g\)