S3 Redox

Question 1

Explain why this is a redox reaction.

Answer 1

Element 1 is reduced. Its oxidation number decreases from ___ in reactant 1 to ____ in product 1.
Element 2 is oxidised. Its oxidation number increases from ___ in reactant 2 to ___ in product 2.
Since reduction and oxidation occurs simultaneously, it is a redox reaction.

Question 2

What is the definition of oxidation? (4)

Answer 2

1) oxygen gain
2) hydrogen loss
3) electron loss
4) increase in oxidation number

Question 3

Define reduction. (4)

Answer 3

1) oxygen loss
2) hydrogen gain
3) electron gain
4) decrease in oxidation number

Question 4

Define oxidising agent.

Answer 4

It brings about oxidation in other substances, but it is reduced itself.

Question 5

What is the function of oxidising agents?

Answer 5

Used to test for reducing agent

Question 6

What are 2 examples of oxidising agent?

Answer 6

1) acidified potassium dichromate (VI) - K2Cr2O7

2) acidified potassium manganate (VII) - KMNO4

Question 7

What can be observed from acidified potassium dichromate (VI)?

Answer 7

It changes from orange to green in presence of reducing agent

Question 8

What can be observed from acidified potassium manganate (VII) (KMNO4)?

Answer 8

Changes from purple to pale pink/colorless

Question 9

define reducing agents.

Answer 9

Brings about reduction in other substances but it is oxidised itself.

Question 10

What is the function of reducing agents?

Answer 10

Test for oxidising agent

Question 11

What is an example of reducing agent and its observation?

Answer 11

Aqueous potassium iodide

Changes from colorless to brown in presence of oxidising agent

Question 12

What is the oxidation number of elements?

Answer 12

0

Question 13

What is the oxidation number of group ions? Group I, group II ETC

Answer 13

+1,+2,+3 respectively

Question 14

What is the oxidation number of oxygen?

Answer 14

Usually -2,

-1 in peroxides and fluorine

Question 15

What is the oxidation number of hydrogen?

Answer 15

Usually +1

-1 in metal hydrides

Question 16

What are definite non-redox reactions? (2)

Answer 16

1) precipitation reaction

2) neutralisation reaction

Question 17

What are strengths of oxidising and reducing agents?

Answer 17

1) the more easily a substance gains electrons, the more powerful an oxidising agent is. (High oxidation number)
2) the more easily a substance loses its electrons, the more powerful a reducing it is (low oxidation number), thus very reactive metals are powerful reducing agents.