Confusion with the formula M1V1=M2V2

[405318478]

I don't understand in dilution, when a question states that, for example, when a 10mL solution is diluted with 20mL, is the final volume 30mL or 20mL? Would the "final" volume that would be used in the equation be the total volume of the final solution, or the amount added?

[Aarja Pavade 1H]

The final volume (V2) would be the sum of the initial volume (10 mL) and what was added to the solution (20 mL). Thus, the final volume would be 30 mL.

[chrisleung-2J]

It depends on how the problem is worded. If a 10mL solution is diluted WITH 20mL, I believe that the final volume would be 30mL. However, if the 10mL solution is diluted TO 20mL, the final volume would be 20mL. In either case, you need to use the final total volume of the solution after the dilution has occurred for V2 in the formula, NOT the volume of water added to dilute the solution.

[Bradley Whitworth 4B]

The final volume would be the total amount added plus the original amount. If a problem says 10ml is diluted WITH 20ml that seems to imply that 20ml are being added to the original 10ml making your final volume 30ml.

[madawy]

That is correct! The equation is still equal since the Molarity also changes proportionally... so even though V1 is 10mL and V2 is 30mL, the molarity ed shift so that M1V1=M2V2 still.