What is the molarity of a solution that contains 0.505 mol KCl (molar mass = 74.55 g/mol) in 7.98 L of solution?

c

=

0.0253 M

Explanation:

Molarity is a measure of a solution's concentration in terms of how many moles of solute it contains per liter of solution.

So, in essence, if you have the number of moles of solute, like you do here, and the total volume of the solution expressed in liters, you can find how many moles of solute you get per liter, i.e. the molarity of the solution.

Keeping in mind the fact that the moles of solute are distributed evenly in any given volume of the solution, you can say that because  

7.98 L

of solution contain  

0.202

moles of solute, which in your case is potassium chloride,  

KCl

,  

1 L

of this solution will contain

1

L

⋅

0.202 moles KCl

7.98

L

=

0.0253 moles KCl

So, if your solution contains  

0.0253

moles of potassium chloride per liter, it follows that its molarity is equal to

c

=

0.0253 M

Here  

M

is equivalent to  

mol/L

, or molar.