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Electrolytic Refining

Electrolytic refining is the method of obtaining a pure metal by using electricity in an electrolytic cell.

In one line: Impure anode gives, pure cathode gets.

Practice This Concept

Understand it

In this process, the impure metal is made the anode and a thin sheet of the pure metal is the cathode.
Metal ions from the anode go into the solution and deposit on the cathode as pure metal.
Insoluble impurities settle down as anode mud.
This method is commonly used for copper.

Example

Impure copper is refined to obtain pure copper for electrical use.

Rule to remember

Rule: in electrolytic refining, the impure metal is the anode, the pure metal sheet is the cathode, and insoluble impurities form anode mud.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

1In copper refining, the impure copper anode slowly dissolves.
2Copper ions move through the solution and deposit on the pure copper cathode, making it thicker and purer.

Method you can reuse

1Identify the impure metal.
2Make it the anode.
3Place a pure metal sheet as cathode.
4Pass current.
5Metal from anode dissolves and deposits on cathode.
6Impurities collect as anode mud.

Visual tip

A labelled cell diagram with anode, cathode, electrolyte, ion movement, and anode mud is essential for this topic.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

In electrolytic refining of copper, where do insoluble impurities collect during the process?

Think first, then show answer

They collect below the anode as anode mud, because they do not dissolve and do not deposit on the cathode.

Common wrong answer

A common wrong answer is to say the cathode dissolves, but in refining the impure anode dissolves while the cathode gains pure metal.

Don't mix this up

Students often mix up anode and cathode roles or think all impurities move to the cathode.

Exam tip

Remember: impure metal at anode, pure metal at cathode, anode mud at the bottom.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Questions may ask the purpose of the anode, the role of electrolyte, the name of anode mud, or why purification becomes possible.

1
Enough for 1 mark
Electrolytic refining is the method of obtaining a pure metal by using electricity in an electrolytic cell.
2
Add for 2 marks
Example: Impure copper is refined to obtain pure copper for electrical use.
3
Add for 3 marks
In this process, the impure metal is made the anode and a thin sheet of the pure metal is the cathode.

MCQ Quiz

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