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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
=> \(\left\{{}\begin{matrix}n_{NaOH\left(dư\right)}=0,01\left(mol\right)\\n_{Na_2SO_4}=0,04\left(mol\right)\end{matrix}\right.\)
=> \(\left\{{}\begin{matrix}m_{NaOH\left(dư\right)}=0,01.40=0,4\left(g\right)\\m_{Na_2SO_4}=0,04.142=5,68\left(g\right)\end{matrix}\right.\)
a) \(Pt:Fe+H_2SO_4\rightarrow FeSO_4+H_2\)
b) \(n_{Fe}=\dfrac{0,56}{56}=0,01mol\)
Theo pt: \(n_{FeSO_4}=n_{Fe}=0,01mol\)
\(\Rightarrow m_{FeSO_4}=0,01.152=1,52g\)
Theo pt: \(n_{H_2}=n_{Fe}=0,01mol\)
\(\Rightarrow V_{H_2}=0,01.22,4=0,224lít\)
c) \(Theopt:nH_2SO_4=n_{Fe}=0,01mol\)
\(\Rightarrow m_{H_2SO_4}=0,01.98=0,98g\)
\(\Rightarrow m_{ddH_2SO_4}=\dfrac{0,98.100}{19,6}=5g\)
a, \(n_K=\dfrac{3,9}{39}=0,1\left(mol\right)\)
PTHH: 2K + 2H2O ---> 2KOH + H2
0,1---------------->0,1----->0,05
\(m_{ct}=m_{KOH}=0,1.56=5,6\left(g\right)\\ m_{dd}=m_K+m_{H_2O}-m_{H_2}=96,2+3,9-0,05.2=100\left(g\right)\)
\(C\%_{KOH}=\dfrac{5,6}{100}.100\%=5,6\%\\ b,m_{dd}=100+50=150\left(g\right)\\ C\%_{KOH}=\dfrac{5,6}{150}.100\%=3,37\%\)
c, Gọi \(m_{H_2O}=a\left(g\right)\)
\(\Rightarrow C\%_{KOH}=\dfrac{5,6}{100+a}.100\%=2,8\%\\ \Leftrightarrow a=100\left(g\right)\)
d, Gọi \(m_{KOH}=a\left(g\right)\)
\(\Rightarrow C\%_{KOH}=\dfrac{5,6+a}{100+a}.100\%=22,4\%\\ \Leftrightarrow a=21,65\left(g\right)\)
\(a,m_{ct}=30\left(g\right)\\ m_{dm}=120\left(g\right)\\ m_{dd}=120+30=150\left(g\right)\\ b,C\%_{đường}=\dfrac{30}{150}.100\%=20\%\\ c,C\%_{đường}=\dfrac{30}{150+50}.100\%=15\%\)
\(d,m_{dd}=\dfrac{30}{10\%}=300\left(g\right)\\ m_{H_2O\left(thêm\right)}=300-150=150\left(g\right)\)
e, Gọi \(m_{đường\left(thêm\right)}=a\left(g\right)\)
\(\Rightarrow C\%=\dfrac{30+a}{150+a}.100\%=30\%\\ \Leftrightarrow a=21,4285\left(g\right)\)
\(n_{CaCO_3}=\dfrac{7}{100}=0,07\left(mol\right)\)
\(n_{HCl}=\dfrac{5,475}{36,5}=0,15\left(mol\right)\)
PTHH: CaCO3 + 2HCl --> CaCl2 + CO2 + H2O
Xét \(\dfrac{n_{CaCO_3}}{1}=0,07< \dfrac{n_{HCl}}{2}=0,075\)
=> HCl dư
Do đó, ta có:
PTHH: CaCO3 + 2HCl --> CaCl2 + CO2 + H2O
_______0,075<---0,15__________________________(mol)
=> \(m_{CaCO_3\left(cầnthêm\right)}=\left(0,075-0,07\right).100=0,5\left(g\right)\)
Ta có: \(n_{O_2}=\dfrac{4,48}{22,4}=0,2\left(mol\right)\)
a, PT: \(4Na+O_2\underrightarrow{t^o}2Na_2O\)
______0,8___0,2___0,4 (mol)
b, a = mNa = 0,8.23 = 18,4 (g)
c, mNaOH = 0,4.40 = 16 (g)
\(\Rightarrow C\%_{NaOH}=\dfrac{16}{150}.100\%\approx10,67\%\)
Bạn tham khảo nhé!
\(n_C=\dfrac{1.2}{12}=0.1\left(mol\right)\)
\(C+O_2\underrightarrow{^{^{t^0}}}CO_2\)
\(0.1.....0.1\)
\(V_{O_2}=0.1\cdot22.4=2.24\left(l\right)\)
nC=1,2/12=0,1(mol)
PTHH:C + O2 -to-> CO2
0,1________0,1____0,1
V(O2,đktc)=0,1 x 22,4=2,24(l)
Bài 5:
Ta có: \(n_P=\dfrac{6,2}{31}=0,2\left(mol\right)\)
a, PT: \(4P+5O_2\underrightarrow{t^o}2P_2O_5\)
_____0,2__0,25__0,1 (mol)
b, VO2 = 0,25.22,4 = 5,6 (l)
c, PT: \(P_2O_5+3H_2O\rightarrow2H_3PO_4\)
______0,1______________0,2 (mol)
\(\Rightarrow m_{H_3PO_4}=0,2.98=19,6\left(g\right)\)
\(\Rightarrow C\%_{H_3PO_4}=\dfrac{19,6}{120}.100\%\approx16,33\text{ }\%\)
Bạn tham khảo nhé!
Gọi x là số mol Na. (x>0)
PTHH: Na + H2O -> NaOH + 1/2 H2
x________________x(mol)
=> mNa=23x(g); mNaOH=40x(g); mH2=x(g)
=> mddNaOH=23x+33,46-x=33,46+22x(g)
Vì dd bazo thu được nồng độ 8%:
=> \(\dfrac{40x}{33,46+22x}.100\%=8\%\\ \Leftrightarrow x=0,07\\ \rightarrow mNa=23.0,07=1,61\left(g\right)\)
=> Cần 1,61 gam Na.
nNa = a (mol)
Na + H2O => NaOH + 1/2H2
a........................a.............0.5a
mNaOH = 40a (g)
mdd NaOH = 23a + 33.46 - 0.5a * 2 = 22a + 33.46 (g)
C%NaOH = 40a/(22a+33.46) * 100% = 8%
=> a = 0.07
mNa = 0.07*23=1.61(g)