1. Gaseous acetylene (C2H2) reacts with oxygen gas to form gaseous carbon dioxide and gaseous water. 2. Chlorine gas reacts with aqueous potassium iodide to form solid iodine and aqueous potassium chloride. 3. Solid lithium oxide reacts with liquid water to form aqueous lithium hydroxide. 4. Gaseous carbon monoxide reacts with oxygen gas to form carbon dioxide gas.