In chemistry, ‘aq’ stands for aqueous. This term is used to indicate that a substance is dissolved in water. When you see a compound written as ‘X (aq)’, it means that X is in a water solution. For example, sodium chloride in water can be represented as NaCl(aq).
Water is often referred to as the universal solvent, meaning it can dissolve a wide variety of substances. The ‘aq’ notation is important because it signifies the state of the reactants or products in a chemical reaction, indicating that they are in solution, which can influence the reaction outcomes.