Electrolytic refining is a process used to purify metals like copper. Let's break down the process step by step:

Step 1: Setup
In electrolytic refining of copper:

• A thick block of impure copper (blister copper) is made the anode.
• A thin strip of pure copper is made the cathode.
• The electrolyte is an acidified solution of copper sulfate ($\mathrm{CuSO}4$). The acidification (usually with sulfuric acid) helps increase conductivity.

Step 2: Electrolysis
When electric current is passed:

• At the anode (impure Cu): Oxidation occurs. Copper atoms lose electrons and go into solution as copper ions: $\mathrm{Cu}\to \mathrm{Cu}\mathrm{2+}+2e^{-}$
• At the cathode (pure Cu): Reduction occurs. Copper ions from the solution gain electrons and get deposited as pure copper: $\mathrm{Cu}\mathrm{2+}+2e^{-}\to \mathrm{Cu}$

Step 3: Handling Impurities
Impurities in the blister copper anode can be of two types:

• More active metals (like Fe, Zn): These also dissolve at the anode but remain in solution because their reduction potentials are less than copper's, so they don't deposit at the cathode.
• Less active metals (like Ag, Au) and inert materials: These do not dissolve and settle down as anode mud.

Now, evaluating the given statements:

• "Impurities settle as anode mud": Correct. Less active impurities like silver and gold form anode mud.
• "Impure Cu strip is used as cathode": Incorrect. The cathode is a thin strip of pure copper.
• "Acidified aqueous CuSO₄ is used as electrolyte": Correct. Acidified copper sulfate solution is the electrolyte.
• "Pure Cu deposits at cathode": Correct. Reduction of Cu²⁺ ions at the cathode gives pure copper deposit.

Related Topics & Formulae

Faraday's Laws of Electrolysis:
The amount of substance deposited or dissolved at an electrode is proportional to the charge passed.

First Law: $m=Z\times Q$, where $m$ is mass deposited, $Z$ is electrochemical equivalent, $Q$ is charge.
Second Law: For same charge, masses deposited are proportional to their chemical equivalents.

Electrochemical Series:
Metals with lower reduction potentials are more likely to oxidize (anode dissolution), while those with higher reduction potentials are reduced (cathode deposition).