Topic 3 Redox

Question 1

What is a disproportionation reaction?

Answer 1

The same species being oxidised and reduced in the same reaction simultaneously

Question 2

What is a redox reaction?

Answer 2

OILRIG
Ox is loss of electrons
Reduce is gain of electrons

Question 3

What is ClO- called?

Answer 3

Chlorate (I) ion

Question 4

How to determine oxidising power of an agent?

Answer 4

Higher oxidising number change in the other reactant
eg FeCl3 makes Fe 3+, FeI2 makes Fe 2+. Higher ox num in Fe 3+ so Cl is a stronger oxidising agent.

Question 5

How is BeCl2 bonded?

Answer 5

It is simple covalent bonding
Since Be is very polarising due to small ionic radius

Question 6

How does BaO + H2SO4 react?

Answer 6

Very briefly
Stops once its starts
Since BaSO4 is very insoluble

Question 7

How does BaO + HNO3 react?

Answer 7

To completion
Since Ba(NO3)2 is very soluble

Question 8

Deduce the half equation for oxidation of ethane-1,2,-diol to ethanedioic acid.
given
3(CH2OH)2 + 4Cr2O7 2- + 32H+ -> 3(COOH)2 + 8Cr 3+ + 22H2O

Answer 8

(CH2OH)2 + 2H2O -> (COOH)2 + 8H+ + 8e-

Question 9

What is a chromate(VI) ion and a dichromate(VI) ion?

Answer 9

CrO4^2- and Cr2O7^- !!

Question 10

An excess of aqueous KBr was added to chlorine water and the solution turned orange. Write an equation for this reaction. (1 mark)

Answer 10

Cl2 + 2Br- -> Br2 + 2Cl-

Question 11

In a solution of Br- and Cl-, silver nitrate solution then excess dilute ammonia is added. Precipitate forms and some is dissolved. Explain why. (3 marks)

Answer 11

AgBr and AgCl formed
Only AgCl can dissolve in dilute ammonia
AgBr cannot dissolve in dilute ammonia

Question 12

What is the ionic equation when chlorine is added to hot aqueous sodium hydroxide solution. (1 mark)

Answer 12

3Cl2 + 6OH- -> 5Cl- + ClO3- + 3H2O

Question 13

Balance
Hg (l) + HNO3 (aq) -> Hg(NO3)2 (aq) + NO (g) + H2O (aq)

Answer 13

3 8 8 2 4