Which salts are formed when sulfuric acid reacts with metals?

Alloys are homogeneous mixtures of a metal with a metal or non-metal. Which among the following alloys contains a non-metal as one of its constituents?

Which among the following statements is incorrect for magnesium metal?

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?

Metals are refined by using different methods. Which of the following metals are refined by electrolytic refining?
$(i)$ $Au$
$(ii)$ $Cu$
$(iii)$ $Na$
$(iv)$ $K$

What is ammonium hydroxide $(NH_4OH)$?