Volume when diluting solutions

[Amanda Wong 3D]

How do you know when to use the given volume to determine the new volume? For example some problems are solved like 0.1M(0.2L)= 0.01M(0.2L +V) to find the amount of water needed to dilute a solution but others are solved like 0.1M(0.2L)= 0.01M(V). When would you use one or the other?

[Deep Mehta]

This depends on what is given in the problem. If they are adding volume to a beaker that already contains a certain amount of water, you would utilize this: 0.1M(0.2L)= 0.01M(0.2L +V). Otherwise, you would utilize 0.1M(0.2L)= 0.01M(V) since it is a simple dilution with no other strings attached. Hope this helps!