80.0mL of a 2.00M KNO3 solution using a 4.00M KNO3 solution

Question

determine the volume in milliliters

Answer 1

I am assuming that you are doing a simple dilution...

 

The equation for dilution is M₁V₁=M₂V₂, where M and V represent the molarity and volume of each solution.

 

So, in your case, you have:

 

(80.0mL)(2.00M) = (xmL)(4.00M)

 

Solving the equation, you get x = 40.0mL of 4.00M solution needed... so to complete the dilution, you will need to take 40.0mL of the concentrated solution and add water until a final volume of 80.0mL is reached.

 

You should also  notice that you are going from 4M to 2M... you want to halve the concentration, so you need to double the volume by adding water.