The process employed for the purification of copper with cuprous oxide as the impurity is (a) polling (b) liquation (c) electrolytic process (d) oxidation

When we talk about the purification of copper, especially when contaminated with cuprous oxide, the most efficient method is the electrolytic process. This method involves using an electric current to drive a non-spontaneous chemical reaction. In simple terms, impure copper is transformed into pure copper through electrochemical reactions.

Let's delve into this further: the impure copper serves as the anode and is placed in a solution called the electrolyte. Electricity is passed through, dissolving the impure copper and allowing the pure copper to be redeposited onto a cathode. During this process, the cuprous oxide and other impurities are either left behind in the solution or form sludge at the bottom of the tank. The result is a high purity copper at the cathode, free from its original impurities.

Polling might sound unfamiliar, but it's a quite straightforward method used in metallurgy to refine specific metals like copper. In polling, the molten metal is stirred or agitated using green wood or poles (hence the name 'pole-ing'). This action introduces hydrocarbon gases into the molten metal, which react with the oxygen present to form carbon dioxide or monoxide. This reaction can reduce metal oxides like cuprous oxide to their pure metal form.

Common Polling Outcomes

• Reduction of metal oxides to pure metals
• Removal of gas impurities due to the agitation

This method is most effective when removing gases or oxides but is not as comprehensive as the electrolytic process for purifying copper.

Liquation might seem similar to melting, but it serves a particular purpose. This technique utilizes the fact that different metals and impurities have different melting points. It's based on controlled heating of the metal mixture, where the metal with the lower melting point moves towards the heat source and can then be separated out.

Picture this: a mix of metals is slowly heated, and as the temperature reaches a specific point, one metal liquefies and flows away, leaving the higher melting-point metal behind. Although liquation is an effective method for certain situations, it is not practical for removing cuprous oxide impurities from copper due to the similar melting points.

Oxidation is a fundamental chemical process used also in metallurgy to cleanse metals from specific impurities. It essentially involves the impurities in the metal reacting with oxygen to form their corresponding oxides. These oxides are usually less dense than the molten metal and can float to the surface, making them easy to remove.

In the purification of copper, if an impurity were simply another metal, it might oxidize quicker than copper and can be skimmed off as it floats up. However, with something like cuprous oxide already in the copper, additional oxidation won't serve the purpose of purification. As such, the oxidation process would not be applicable or adequate in the context of purifying copper that contains cuprous oxide as an impurity.