Physical Chemistry and Transition Element

Question 1

write the method of writing half equations
and use the example of VO(2+) –> VO2 (+)

Answer 1

1. Calculate oxidation states on each side
   VO (2+) = +4
   VO2(+) = +5
2. Balance element changing oxidation state (already balanced)
3. Sort out electrons. if the oxidation state becomes more -tive then gains elec, more +ve loses elec
   VO(2+) –> VO2(+) + e- (V becomes 1 more positive so one elec lost)
4. Sort out Oxygens, for every O gained/ lot add/remove one H2O molecule
5. Sort out Hs. for every H gained/lost, add/remove 1 H+ ion
6. check if the total elec charge on the left equals right then YAY

Question 2

write the half equation for Pb (4+) –> Pb (2+)

Answer 2

Pb (4+) + 2e(-) – Pb (2+)

Question 3

write the half equation for SO4 (2-) –> H2S

Answer 3

SO4 (2-) + 8e(-) + 10H(+) –> H2S + 4H2O

Question 4

write the half equation for this reaction
SO2 + 2H2) + 2Cu(2+) + 2Cl- –> SO4(2-) + 4H+ + 2CuCl

Answer 4

SO2 + 2H2O + 2Cu(2+) + 2Cl(-) –> SO4(2-) + 4H+ + 2CuCl

Question 5

write the half equation for the reduction of MnO4(-) ions to Mn(2+)

Answer 5

MnO4 + 8H+ + 5e- –Mn(2+) + 4H2O

Question 6

how do you calculate the amount of iron in an iron tablet from a potassium manganate titration

Answer 6

n(MnO4-) = C x V / 1000 = ans
ans x 5 = n(Fe)2+
M = n x Mr –> M(Fe) per tablet