Question

A solution of NaOH contains 7.2 g of NaOH per 100 mL. What is the molarity of the NaOH solution?

a) 0.2 M
b) 0.4 M
c) 0.6 M
d) 0.8 M

Answer 1

To find the molarity of the NaOH solution, convert the mass of NaOH to moles and the volume of the solution to liters. Divide the number of moles by the volume in liters to get the molarity.

Step-by-step explanation:

To find the molarity of the NaOH solution, we first need to convert the mass of NaOH to moles. The molar mass of NaOH is 40.0 g/mol, so the number of moles of NaOH is calculated as :

7.2 g NaOH x (1 mol NaOH / 40.0 g NaOH) = 0.18 mol NaOH

Next, we convert the volume of the solution from mL to L:

100 mL x (1 L / 1000 mL) = 0.1 L

Finally, we divide the number of moles by the volume in liters to get the molarity:

Molarity = 0.18 mol NaOH / 0.1 L = 1.8 M NaOH

Therefore, the molarity of the NaOH solution is 1.8 M, which is not one of the given options. So none of the options (a) 0.2 M, (b) 0.4 M, (c) 0.6 M, or (d) 0.8 M are correct.