Question

What is the concentration (M) of KCl in a solution made by mixing 30.0 mL of 0.100 M KCl with 50.0 mL of 0.100 M KCl?

Answer 1

The concentration will be 0.100 M KCl.

Explanation:

Adding two solutions of the same concentration will give a solution of the same concentration as the original two solutions.

Just in case there was a typo in the problem, let's do the math as if we did not have this trivial case.

The first solution contains 0.03 L of 0.1 mol/L KCl so it contains

`0.03L(0.1mol KCl)/(L)=0.003` mole KCl.

The second solution contains 0.05 L of 0.1mol/L KCl so it contains

`0.05L(0.1mol KCl)/(L)=0.005` mole KCl.

The total solution contains 0.003 + 0.005 = 0.008 moles of KCl and the total volume of the solution will be 0.03 + 0.05 = 0.08 L of solution. The concentration of KCl is then

`[KCl]=(0.008 mol)/(0.08 L)= 0.100M` KCl