Which color solution is formed when sulfur dioxide gas reduces an acidic potassium dichromate solution?

Which process occurs at the cathode during the process of electrolysis?

You could have noted that when copper powder is heated in a china dish, the surface of copper powder becomes coated with black coloured substance.
$(i)$ Why has this black coloured substance formed?
$(ii)$ What is this black substance?
$(iii)$ Write the chemical equation of the reaction that takes place.

State one industrial application of the reduction process.

When sulfur dioxide gas reacts with hydrogen sulfide gas,sulfur is formed. Which of the following statements about sulfur dioxide is incorrect for this reaction?

What happens when copper oxide is heated in the presence of dihydrogen gas?