5.3.1 k-l redox reactions

Question 1

What is the oxidising agent for the reaction of Fe2+ –> Fe 3+? What does it reduce to?

What is the change in the oxidation state of the agent?

Answer 1

MnO4- –>Mn2+

+7 –> +2

Question 2

What is the reducing agent for the reaction of Fe3+–> Fe2+? What does it oxidise to?

What is the change in the oxidation state of the agent?

Answer 2

2I- –> I2

-1 –> 0

Question 3

What is the oxidising agent for Cr3+ –> CrO42-? What is it reduced to?

What is the change in the oxidation state of the Cr3+?

Answer 3

H2O2 –> 2OH-

+3 –> +6

Question 4

What is the reducing agent for Cr2O72- –>Cr3+? What is it oxidised to?

What is the change in the oxidation state of the agent?

What is the change in the oxidation state of the Cr2O72-?

Answer 4

Zn –> Zn2+

0 –> +2

+6–> +3

Question 5

What is the reducing agent for Cr3+ –> Cr2+-? What is it oxidised to?

Answer 5

Zn –> Zn2+

Question 6

What is the reducing agent for Cu2+ –> Cu? What is it oxidised to?

What is the change in oxidation states for the agent

Answer 6

4I- –> I2 + 2CuI

-1 –> 0

Question 7

What does Cu+ react with to be simultaneously reduced and oxidised? What is the product not containing Cu?

Answer 7

H2SO4

H2O

Question 8

In the equation where Fe2+ is oxidised, what is the starting and end point colour?

Answer 8

Deep purple –> colourless (pale pink)

Question 9

In the equation where Fe3+ is reduced, what is the starting and end point colour?

Answer 9

Hard to tell because orange brown–> brown – would need indicator here

Question 10

In the equation where Cr2O72- is reduced, what is the starting and end point colour? What happens when excess zinc is added?

Answer 10

orange –> green

further colour change to pale blue

Question 11

In the equation where Cu2+ is reduced, what is the starting and end point colour?

Answer 11

pale blue –> brown solution of I2 and white precipitate of CuI

Question 12

When Cu2O is reduced by H2SO4 what is formed, what is this colour?

Answer 12

Cu (s) brown precipitate

Question 13

When Cu2O is oxidised by H2SO4 what is formed, what is this colour?

Answer 13

CuSO4 – pale blue solution.

Question 14

What is the formula of the copper complex that is deep blue in solution?

Answer 14

[Cu(NH3)4(H2O)2]2+

Question 15

What is the formula of the copper complex that forms a light blue precipitate? What is its simple formula?

Answer 15

[Cu(H2O)4(OH)2]

Cu(OH)2