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a, \(2Na+2H_2O\rightarrow2NaOH+H_2\)
b, \(n_{Na}=\dfrac{4,6}{23}=0,2\left(mol\right)\)
Theo PT: \(n_{NaOH}=n_{Na}=0,2\left(mol\right)\Rightarrow m_{NaOH}=0,2.40=8\left(g\right)\)
c, \(C_{M_{NaOH}}=\dfrac{0,2}{0,2}=1\left(M\right)\)
\(Na+H_2O->NaOH+\dfrac{1}{2}H_2\\ a.n_{Na}=\dfrac{m_1}{23}\left(mol\right)\\ m_{ddsau}=\dfrac{m_1}{23}+m_2-\dfrac{m_1}{46}=\dfrac{m_1}{46}+m_2\left(g\right)\\ C\%_B=\dfrac{\dfrac{40}{23}m_1}{\dfrac{m_1}{46}+m_2}\cdot100\%.\\ b.C_M=\dfrac{10dC\%}{M}=10\cdot1,2\cdot\dfrac{0,05}{40}=0,015\left(M\right)\)
\(Na+H_2O->NaOH+\dfrac{1}{2}H_2\\ a.n_{Na}=\dfrac{m_1}{23}\left(mol\right)\\ m_{ddsau}=m_1+m_2-\dfrac{m_1}{23}=\dfrac{22}{23}m_1+m_2\left(g\right)\\ C\%_B=\dfrac{\dfrac{40}{23}m_1}{\dfrac{22}{23}m_1+m_2}\cdot100\%.\\ b.C_M=\dfrac{10dC\%}{M}=10\cdot1,2\cdot\dfrac{0,05}{40}=0,015\left(M\right)\)
a, \(Na_2O+H_2O\rightarrow2NaOH\)
Ta có: \(n_{Na_2O}=\dfrac{3,1}{62}=0,05\left(mol\right)\)
Theo PT: \(n_{NaOH}=2n_{Na_2O}=0,1\left(mol\right)\)
m dd sau pư = 3,1 + 50 = 53,1 (g)
\(\Rightarrow C\%_{NaOH}=\dfrac{0,1.40}{53,1}.100\%\approx7,53\%\)
b, \(2Na+2H_2O\rightarrow2NaOH+H_2\)
Ta có: \(n_{Na}=\dfrac{4,6}{23}=0,2\left(mol\right)\)
Theo PT: \(\left\{{}\begin{matrix}n_{NaOH}=n_{Na}=0,2\left(mol\right)\\n_{H_2}=\dfrac{1}{2}n_{Na}=0,1\left(mol\right)\end{matrix}\right.\)
Ta có: m dd sau pư = 4,6 + 95,6 - 0,1.2 = 100 (g)
\(\Rightarrow C\%_{NaOH}=\dfrac{0,2.40}{100}.100\%=8\%\)
Na--------> Na2O -----------> NaOH
0,2............0,1...........................0,2
Bảo toàn nguyên tố Na: \(n_{NaOH}=n_{Na}=\dfrac{4,6}{23}=0,2\left(mol\right)\)
=> \(C\%_{NaOH}=\dfrac{0,2.40}{0,1.62+190}.100=4,08\%\)
\(a,m_{dd}=\dfrac{5}{12\%}=\dfrac{125}{3}\left(g\right)\\ b,m_{dd}=\dfrac{4}{7,3\%}=\dfrac{4000}{73}\left(g\right)\\ c,m_{NaOH}=0,5.40=20\left(g\right)\\ m_{dd}=\dfrac{20}{10\%}=200\left(g\right)\)
a, \(2Na+2H_2O\rightarrow2NaOH+H_2\)
Ta có: \(n_{Na}=\dfrac{2,3}{23}=0,1\left(mol\right)\)
\(n_{H_2O}=\dfrac{200}{18}=\dfrac{100}{9}\left(mol\right)\)
Xét tỉ lệ: \(\dfrac{0,1}{2}< \dfrac{\dfrac{100}{9}}{2}\), ta được H2O dư.
Theo PT: \(n_{H_2}=\dfrac{1}{2}n_{Na}=0,05\left(mol\right)\Rightarrow V_{H_2}=0,05.22,4=1,12\left(l\right)\)
b, Theo PT: \(n_{NaOH}=n_{Na}=0,1\left(mol\right)\)
Ta có: m dd sau pư = 2,3 + 100 - 0,05.2 = 102,2 (g)
\(\Rightarrow C\%_{NaOH}=\dfrac{0,1.40}{102,2}.100\%\approx3,91\%\)
c, - Dung dịch làm quỳ tím hóa xanh.
\(n_{Na}=\dfrac{2,3}{23}=0,1\left(mol\right)\\ 2Na+2H_2O\rightarrow2NaOH+H_2\\ n_{H_2}=\dfrac{0,1}{2}=0,05\left(mol\right);n_{NaOH}=n_{Na}=0,1\left(mol\right)\\ a,V=V_{H_2\left(đktc\right)}=0,05.22,4=1,12\left(l\right)\\ b,m_{ddNaOH}=m_{Na}+m_{H_2O}-m_{H_2}=2,3+200-0,05.2=202,2\left(g\right)\\ C\%_{ddNaOH}=\dfrac{40.0,1}{202,2}.100\approx1,978\%\\ c,NaOH-Tính.bazo\Rightarrow Quỳ.tím.hoá.xanh\)
\(C\%_{ddNaOH\left(thu.được\right)}=\dfrac{20}{20+150}.100\%\approx11,765\%\)
\(n_{Na}=\dfrac{6,9}{23}=0,3mol\)
\(n_{H_2O}=\dfrac{150}{18}=\dfrac{25}{3}mol\)
\(2Na+2H_2O\rightarrow2NaOH+H_2\)
\(0,3\) \(\dfrac{25}{3}\) 0 0
0,3 0,3 0,3 0,15
\(m_{NaOH}=0,3\cdot40=12g\)
\(m_{H_2}=0,15\cdot2=0,3g\)
\(m_{ddNaOH}=6,9+150-0,3=156,6g\)
\(C\%=\dfrac{12}{156,6}\cdot100\%=7,66\%\)
\(2Na+2H_2O\rightarrow2NaOH+H_2\uparrow\)
\(nNa=\dfrac{6,9}{23}=0,3\left(mol\right)\)
\(nH_2O=\dfrac{150}{18}=8,3\left(mol\right)\)
Xét tỉ lê :
\(\dfrac{0,3}{2}< \dfrac{8,3}{2}\)
H2O dư , tính số mol dd theo số mol của Na
\(\Rightarrow nNaOH=nNa=0,3\left(mol\right)\)
\(\Rightarrow mNaOH=0,3.40=12\left(g\right)\)
\(C\%=\dfrac{12}{6,9+150}.100\%=7,64\%\)