You complete a titration and find that you need 2.5 mL of a 0.1M NaOH to neutralize 250 mL of

the river water.

How many moles of NaOH did you use to neutralize the river water?

0.00025 mole

Explanation:

The number of moles of a substance can be mathematically derived from the following formula

1. mass of substance (in grams) / molar mass of substance (in grams/mole)

2. molarity of substance (in mol/dm3) x volume of substance (in dm3)

In this case, the molarity and volume of NaOH are provided, hence, the second formula will be applicable.

2.5 mL of NaOH was used = 0.0025 dm3

Number of mole of NaOH that was used to neutralize the river water:

= 0.1 x 0.0025 = 0.00025 mole

The number of mole of NaOH used to neutralize the river water is 0.00025 mole.