10.0 ml of 1.00 M HCl neutralized 20.0 ml of a NaOH solution. What was the molarity of the NaOH?

0.500 M

Explanation:

The balanced equation for the neutralization reaction is as follows

NaOH + HCl - > NaCl + H2O

Molar ratio of NaOH to HCl is 1:1

Number of moles of NaOH reacted is equal to the number of HCl moles

We can use the following equation

c1v1 = c2v2

Where c1 is concentration and v1 is volume of HCl

c2 is concentration and v2 is volume of NaOH

Substituting the values

1.00 M x 10.0 mL = c2 x 20.0 mL

c2 = 0.500 M

Concentration of NaOH is 0.500 M