1. Prepare the NaOH solution by dissolving approximately 4g of solid NaOH in 200 mL of water. Calculate and record the approximate NaOH concentration (MW = 40.00).
2. To prepare the primary standard, first calculate and record the expected mass of benzoic acid required to react in stoichiometric proportion with 20 mL of the NaOH solution (MW = 122.12). Record this amount.

1. Figure out the molecular weight (formula weight) of NaOH. You have 4 grams of NaOH. The molecular weight is in grams/mole so if you divide grams by grams/mole, you'll end up with moles. It's approximate because NaOH absorbs water and CO2 from the air and the weight is approximate -- not accurate.

2. From #1, you know the approximate number of moles. Benzoic acid has only one hydrogen ion to react with the NaOH, so 1 mole reacts with 1 mole (I'll let you write down the equation and balance it). You have the number of moles from #1 so divide that by the 200 mL of solution to get moles/mL. Since you now know the number of moles you'll need, divide that by moles/mL to get mL.