In a chemical equation which symbol should be used to indicate that a substance is in solution

(aq)

Explanation:

Chemistry majorly involves chemicals which cannot do without reacting or combining with each other to form new products. Chemical substances exist in different states. These states are symbolised in chemistry when writing chemical equations in order to show what state the substance is during the reaction. These symbols are placed in a bracket as a subscript close to the chemical substance being referred to.

(s) is the symbol used to denote a chemical substance in its solid state.

(g) is used to represent a chemical substance in gaseous state.

(l) is used to represent a chemical substance in liquid state.

(aq) is used to denote a chemical substance dissolved in water forming a solution called AQUEOUS.

Hence, the answer to the question is (aq).