Question

How many grams of NaOH are needed to prepare 600.0 mL of a solution with pH = 10.00 at 25 °C?

Answer 1

Answer – Given, pH = 10.0 , volume = 600.0 mL

First we need to calculate the pOH from the pH

pH + pOH = 14

so, pOH = 14-pH

              = 14 – 10

              = 4

Calculation of [OH^-] from the pOH

We know the formula

pOH = - log [OH^-]

so, [OH^-] = 10^-pOH

                 = 10^-4

                 = 1.0*10^-4 M

Calculation of moles of OH^-

We know,

Molarity = moles / L

So, moles = molarity * volume (L)

                 = 1.0*10^-4 M *0.600 L

                 = 6.0*10^-5 moles

We know,

1 moles of NaOH = 1 mole of OH^-

So, moles of NaOH = 6.0*10^-5 moles

Calculation of mass of NaOH

Mass of NaOH = 6.0*10^-5 moles * 40.0 g/mol

                          = 0.0024 g of NaOH

0.0024 grams of NaOH are needed to prepare 600.0 mL of a solution with pH = 10.00 at 25 °C