M1V1=M2V2 is used to calculate what?

• A. Dilution calculations
• B. Solubility
• C. Temperature
• D. pH of solution

Answer: (A)

Dilution calculations rely on conserving the amount of solute; M1V1 = M2V2 expresses that the number of moles stays the same before and after dilution. M stands for molarity (moles per liter) and V for volume, so if you know three of the four values, you can solve for the fourth to predict the final concentration or the needed volumes. For example, starting with 5 mL of a 2.0 M stock and diluting to a final volume of 100 mL gives M2 = (M1V1)/V2 = (2.0 × 5)/100 = 0.10 M. This is exactly what you use for dilution calculations. The other concepts aren’t governed by this relationship: solubility describes how much solute can dissolve, temperature affects many properties including solubility and pH, and pH measures hydrogen ion concentration, not how concentrations change with dilution.