U1-1-2 - Ion-electron and Redox Equations

Question 1

When copying equations from the ECS, which one gets reversed?

Answer 1

Higher one gets reversed (OR read equations anticlockwise)

Question 2

What’s wrong with this redox equation?

Ni(s) + SO₄²⁻(aq) + 2H⁺(aq) + H₂O(l) ⟶ Ni²⁺(aq) + SO₃²⁻(aq) + H₂O(l) + e^–

Answer 2

Any of:

Still has electrons/charges not balanced

Water present on both sides

Question 3

What must be done before these equations can be added up?

Na(s) ⟶ Na⁺(aq) + e⁻

Cl₂(g) + 2e⁻ ⟶ 2Cl⁻(aq)

Answer 3

Electrons must be balanced (top equation x2)

(This is done to balance the charges in the redox equation.)

Question 4

How do you finish writing this type of equation?

Sn³⁺ ⟶ Sn²⁺

Answer 4

Add required no. of electrons to the more positive side.

Sn³⁺ + e⁻ ⟶ Sn²⁺

Question 5

How would you proceed?

Answer 5

Balance non-oxygen atoms

Question 6

How would you proceed?

Answer 6

Balance oxygen atoms by adding required no. of H₂O molecules

Question 7

How would you proceed?

Answer 7

Balance no. of H atoms by adding required no. of H⁺ ions

Question 8

How would you proceed?

Answer 8

Add required no. of electrons to the more positive side to balance the charges

Question 9

Suggest a use of oxidising agents

Answer 9

Any of:
* Kill fungi and bacteria
* Inactivate viruses
* Break down coloured compounds (bleaches)

Question 10

Dichromate and permanganate ions are strong oxidising agents in ________ solutions.

Answer 10

acidic

Question 11

The reaction below only works if acid is added. Why?

Answer 11

Acid provides H⁺ ions needed for the reaction