SEC 4 ELECTROLYSIS REVISION

SEC 4 ELECTROLYSIS

REVISION

#1 TIP

Cations move to Cathode

Anions move to Anode during electrolysis

#2 TIP

Electrolysis always gives a metal or hydrogen at the cathode (-)

Electrolysis always gives a non-metal other than hydrogen at anode(+)

# 3 TIP : STARTING WITH A MOLTEN COMPOUND

Molten ionic compound will always give metal at cathode(-) & non-metal at anode(+)

#4 STARTING WITH SOLUTION

A metal or H₂ forms at cathode (-)

1. If the metal is more reactive than H₂, H₂ forms.

2. If a metal is less reactive than H_2, metal forms

A non-metal other than H₂ forms at the anode (+)

1. A concentrated solution of a halide (a chlorine, bromide, iodide) gives chlorine, bromine or iodine at the anode.

2. But if no halide is present, or halide solution is dilute, O₂ forms instead

# 5 TIP

Make sure if you are asked for observations you write about what you see, hear, smell or feel

#6 TIP

Cations will always gain electron at cathode. Hence REDUCTION occurs

#7 TIP

Anions will always give up electrons at anode hence OXIDATION occurs.

REACTIVITY

#8 TIP: DIFFERENT ELECTRODES, DIFFERENT PRODUCTS

The idea of dissolving anode is used in electroplating and refining copper.



#9 TIP: TO ELECTROPLATE METAL OBJECT WITH A COAT OF METAL X

1. Use metal X at anode (+)

2. Use the object as the cathode (-)

3. Use a solution of a soluble compound of X as the the electrolyte

PRACTICE TIME

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