In this video we take a look at the concept of dilutions and the equations associated with dilutions. Any time we are talking about dilutions we use the equation of M₁V₁ = M₂V₂.
M₁ here represents the molarity or concentration before dilution has occurred
V₁ represents the volume before dilution has occurred
M₂ represents the molarity or concentration after dilution
V₂ represents your volume after dilution
Some key things in relation to the variables to one another:
M₁ represents your concentration before dilution. It is more concentrated because we haven’t added water yet. Therefore, M₁ is always a larger value than M₂, it is a larger molarity.
V₂, since that’s the volume after we’ve added water, V₂ will be larger than M₁. Since V₂ represents our final volume after we’ve added water, V₂ equals V₁ plus the amount of water you’ve added. That’s the whole process of dilution, adding water.
In terms of dilution, they’ll refer to two molarities or two volumes for a single compound.
For example, you have 50 ml of 0.100 M NaOH and you are going to dilute it so that you get to a new concentration of 0.012 M NaOH. Realize that we are talking about only one compound the whole time and they have given us two molarities. That’s the key to realizing dilution is occurring - referring to one compound and that one compound is either dealing with two molarities or two volumes right from the beginning of the question.
Now, they also could mention or reference as “mixing or adding water to the solution” which represents a dilution and it’s a signal to you that the dilution formula will most likely be used to answer the question.
Remember, when we talk about dilutions it is just simply adding water to a reaction mixture. It causes our solution to become less concentrated so your M₂ is smaller than your M₁. Because you are adding water, the overall volume increases that’s why your V₂ (your final volume) is bigger than V₁ (your initial volume).