CHEM- ELECTROLYSIS HELP

[Manny]

Hi everyone! If anyone knows how to do questions 20,21, and 22, it would be great if you could show me the working out. The answers are A,D,B. Check the attachment!

[09Ti08]

Question 20:
n(H₂)=3/2=1.5(mol)
I hope you notice the coefficients in front of the electrons, which quickly lead you to the conclusion that: the coefficient in front of H₂is 4, and that of ClO₄^- is 1
So n(ClO₄^-)=1.5/4=0.375(mol)
m(NaClO₄)=0.375*122.5=45.9(g)

Question 21:
2H₂O->2H₂+O₂
n(H2O)=1 mol
So n(gas)=1*2/2+1/2=1.5 mol
V(gas)=1.5*22.4

Question 22:
Formation of H2: 2H⁺+2e- > H2
Notice the coefficients in front of the electrons once again, the coefficient in front of H2 must be 4
n(H2)=1 mol
=> n(ClO4^-)=1/4=0.25 mol
m(KClO4)=0.25*138.6=34.65g

[Manny]

Thanks a bunch 09Ti08!