ONA: Half equations in electrolysis

Question 1

How does an aluminium atom form an aluminium ion?
Tip - Aluminium= G3

Answer 1

• Aluminium loses 3 electrons

Question 2

How would an aluminium ion form an aluminium atom?
Tip - Aluminum = G3

Answer 2

• Aluminum ion gains 3 electrons to form neutral aluminium.
  Go backwards

Question 3

What is the rule for positive ions to form their neutral atoms?

Answer 3

• Positive ions must gain electrons to form their neutral atoms.
  Opposite of what they did to become ion

Question 4

What is the rule for negative ions to form their neutral atoms?

Answer 4

• Negative ions must lose electrons to form neutral ions.
• Opposite of what they did to become ion*

Question 5

What is the “cathode”?

Answer 5

• The cathode is the negatively charged electrode.

Question 6

What ions are attracted to the “cathode”?

Answer 6

• Positive ions are attracted to the cathode.

Question 7

What is the “annode”?

Answer 7

• The annode is the positively charged electrode.

Question 8

What ions are attracted to the “annode”?

Answer 8

• Negative ions are attracted to the annode.

Question 9

What happens to positive ions once they reach the cathode?

Answer 9

• Positive ions gain electrons to form the neutral atom.

Question 10

What happens to negative ions once they reach the annode?

Answer 10

• Negative ions lose electrons to form the neutral atom.

Question 11

What are the 2 TopTips when writing half equations?

Answer 11

1.) Balance atoms/ charge
2.) Remember what existis as molecules.

Question 12

How would you write a magnesium ion gaining 2 electrons at cathode?

Answer 12

Mg²⁺+2e⁻–> Mg

Question 13

How would you write an oxygen ion losing 2 electrons at annode?

Answer 13

2O²⁻—>O₂+4e⁻

Question 14

What are the steps of writing a half equation?

Answer 14

1.) Write what the ion becomes
2.) Add electons
3.) Balnace atoms/ charge

Question 15

What do you need to make sure you write for a neutral atom that exists as a molecule?

Answer 15

• You must write a subscript 2.

Question 16

Where does the electron symbol appear when electrons are lost?

Answer 16

• On the right hand side of the eqaution.

Question 17

What is a neumonic to remember oxidation and reduction in terms of electrons?

Answer 17

Oxidation
Is
Loss
Reduction
Is
Gain

Question 18

Would a calcium ion (Ca²⁺) be reduced or oxidised to form neutral Ca?

Answer 18

• Positive ions gain electrons
• Reduction is gain.
• Calcium ion is reduced.

Question 19

Would a bromide ion (Br⁻) be reduced or oxidised to form neutral Br?

Answer 19

• Negative ions lose electrons.
• Oxidation is loss.
• Bromide ion is oxidised.

Question 20

What reaction occurs at the cathode?
Gain of electrons

Answer 20

• Reduction occurs at cathode

Question 21

What reaction occurs at the anode?
Loss of electrons

Answer 21

• Oxidation occurs at annode.

Question 22

What is being reduced in this equation:
Al³⁺+3e⁻–> Al

Answer 22

• Al³⁺/ aluminium ion

Question 23

What is being oxidised in this equation:
2Br⁻–> Br₂+2e⁻

Answer 23

• Br⁻/ bromide ion

Question 24

What are the products of this reaction:
2Br⁻–> Br₂+2e⁻

Answer 24

Br₂+2e⁻
- Bromine
- 2 electrons lost