### M1V1=M2V2

Posted:

**Sun Oct 06, 2019 6:09 pm**When can you use the equation M1V1=M2V2? Are there certain scenarios where you have to convert to moles in order to solve for dilution problems?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=10&t=46543

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Posted: **Sun Oct 06, 2019 6:09 pm**

When can you use the equation M1V1=M2V2? Are there certain scenarios where you have to convert to moles in order to solve for dilution problems?

Posted: **Sun Oct 06, 2019 6:17 pm**

M1V1=M2V2 is a concept that means the amount of moles in the solution remains constant whether you are changing the concentration of the solution or the volume of the solution. So by adding water to a solution with a certain morality of a certain molecule or ion, you are increasing the volume of the solution which in turn changes the molarity or concentration of that molecule or ion in the solution. You would typically use this equation for dilution problems.

Posted: **Sun Oct 06, 2019 7:45 pm**

You could use this formula in a question like:

If you dilute 300. mL of a 4.00 M solution of CuCl_{2} to 900. mL, what is the new concentration of the solution? (from a step-up session)

First, you'd use your given to figure out what parts of the equation you already have and then just plugging it in.

M1= 4.00 M CuCl_{2}

V1= 300. mL

M2= ?

V2= 900. mL

You would end up getting 4.00 * 300. mL/900. mL = 1.33 M CuCl_{2}

If you dilute 300. mL of a 4.00 M solution of CuCl_{2} to 900. mL, what is the new concentration of the solution? (from a step-up session)

First, you'd use your given to figure out what parts of the equation you already have and then just plugging it in.

M1= 4.00 M CuCl_{2}

V1= 300. mL

M2= ?

V2= 900. mL

You would end up getting 4.00 * 300. mL/900. mL = 1.33 M CuCl_{2}

Posted: **Fri Oct 11, 2019 10:32 pm**

M1= initial molarity

V1= initial volume

M2= final molarity

V2= final volume

M1V1=M2V2 is used to solve for the concentration or volume of the concentrated or dilute solution. Thus, you can use the formula M1V1=M2V2 when you are trying to solve from the initial molarity, initial volume, final molarity, or final volume (if you are given at least three of the following, it is a huge indicator that you should use this formula if you want to find the missing value).

V1= initial volume

M2= final molarity

V2= final volume

M1V1=M2V2 is used to solve for the concentration or volume of the concentrated or dilute solution. Thus, you can use the formula M1V1=M2V2 when you are trying to solve from the initial molarity, initial volume, final molarity, or final volume (if you are given at least three of the following, it is a huge indicator that you should use this formula if you want to find the missing value).

Posted: **Fri Oct 11, 2019 10:56 pm**

During one of the step up sessions, the UA said to use M1V1=M2V2 whenever a dilution is mentioned. However, when you can't identify a dilution is occurring you most likely have to use M= m/v. This may not always be the case, but this is how I would think of it in simplest terms.

Posted: **Sat Oct 12, 2019 12:41 pm**

Molarity is moles/liters. if a question asks you to find moles of a certain substance. Then you could break down M1V1=M2V2 into moles/liters*volume.

Posted: **Sat Oct 12, 2019 12:51 pm**

you can use this equation when you have 3 of these values and need to find the fourth value. for example if you had M1 and M2 and V1 you could use this equation to find V2.

Posted: **Sat Oct 12, 2019 12:55 pm**

When I do these type of problems, I often have to convert the units from grams to moles or milliliters to liters. So make sure you pay attention to the units before you start solving the problems using the equations M1V1=M2V2 and Molarity=moles of solute/liters of solution.

Posted: **Sun Oct 13, 2019 3:55 pm**

This equation can be used when you are given any of the three values needed for the completion of the equation. For example if you are asked to find the V1, you will need to have M1, M2, and V2 in order to be able to use this equation.

Posted: **Sun Oct 13, 2019 5:59 pm**

You may have to convert to moles in a problem that requires the dilution equation if the question is asking for a particular quantity of moles when given a volume of solution of a certain molarity. It is helpful in these situations to remember that molarity of moles over liters.

Posted: **Sun Oct 13, 2019 6:38 pm**

You use this equation during dilution questions. like when you're asked how much of one solution you would need to achieve certain molarity of another volume solution. Anytime you'd be given three of the variables of the equation and asked to find the other.

Posted: **Sun Oct 13, 2019 6:52 pm**

You use M1V1=M2V2 in dilution problems, typically asking for either the concentration or volume in either the initial side or final side of the equation. One to thing to note is to look closely at what the question is asking for. Just because you are given 2 volume measurements and 1 concentration value does not mean you are always using this equation. Ensure that you have concentrations and volumes to work with ensuring that you convert units necessary. For example if grams are given you need to convert them to moles, and if given milliliters, convert to liters.