What is the molarity of a solution that contains 15.0g of naoh per 500.0 ml of solution

0.4 M

Explanation:

Molarity is defined as moles of solute, which in your case is sodium hydroxide,

NaOH

, divided by liters of solution.

molarity

=

moles of solute

liters of solution

Notice that the problem provides you with the volume of the solution, but that the volume is expressed in milliliters,

mL

.

Moreover, you don't have the number of moles of sodium hydroxide, you just have the mass in grams. So, your strategy here will be to

determine how many moles of sodium hydroxide you have in that many grams

convert the volume of the solution from milliliters to liters

So, to get the number of moles of solute, use sodium hydroxide's molar mass, which tells you what the mass of one mole of sodium hydroxide is.

7

g

⋅

1 mole NaOH

40.0

g

=

0.175 moles NaOH

The volume of the solution in liters will be

500

mL

⋅

1 L

1000

mL

=

0.5 L

Therefore, the molarity of the solution will be

c

=

n

V

c

=

0.175 moles

0.5 L

=

0.35 M

Rounded to one sig fig, the answer will be

c

=

0.4 M