Write a balanced chemical equation for each of the following.
1. Solid copper reacts with solid sulfur to form solid copper(I) sulfide.
2. Sulfur dioxide gas reacts with oxygen gas to form sulfur trioxide gas.
3. Aqueous hydrochloric acid reacts with solid manganese(IV) oxide to form aqueous manganese(II) chloride, liquid water, and chlorine gas.
4. Liquid benzene (C6H6) reacts with gaseous oxygen to form carbon dioxide and liquid water.