In the dilution equation C1V1 = C2V2, which quantity is conserved between the two states?

• A. The product of concentration and volume
• B. The sum of concentration and volume
• C. The final volume only
• D. The initial concentration only

Answer: (A)

During dilution, the amount of solute remains the same even though the solution is spread into a larger volume. The product of concentration and volume represents how much solute is present (concentration in mol/L times volume in L gives moles). Since no solute is added or removed and no chemical change occurs, the initial amount of solute equals the final amount, so C1V1 equals C2V2. This means the quantity that stays constant is the product of concentration and volume.

The other ideas don’t stay fixed: adding solvent changes the final volume, and dilution lowers concentration, so the sum of concentration and volume isn’t preserved, nor are the initial or final concentrations alone.