Question

Calculate the molarity of solution given the following information:. . 10.0 g of NaOH were dissolved in 500.0 mL of solution.

Answer 1

Molar mass NaOH = 23 + 16 + 1 => 40.0 g/mol

number of moles:

10.0 g / 40 => 0.25 moles

Volume in liters:

500.0 mL / 1000 => 0.5 L

M = n / V

M = 0.25 / 0.5

M = 0.5 mol/L

hope this helps!

Answer 2

By using the following formulas:
 molarity= no of mol of NaOH/volume
 no of mol of NaOH= mass/molar mass
the molarity of the solution can be easily determined. 
Mass of NaOH= 23+16+1 =40
then put this value in this formula
 no of mol of NaOH= mass/molar mass 
and after calculating the no. of moles. 
put the value in this formula 
 molarity= no of mol of NaOH/volume 
and molarity will be 0.500 M.