Question

Determine the ph of a solution that is 1.35% naoh by mass. assume that the solution has density of 1.01 g/ml.

Answer 1

Answer: -

13.545

Explanation: -

Let the volume of the solution be 1000 mL

Density = 1.04 g/ mL

Mass = density x vol

= 1.04 g/ mL x 1000 mL

= 1040 g

Amount of NaOH =
`(1.35)/(100)` x 1040 g

= 14.04 g

Molar mass of NaOH = 23 x 1 + 16 x 1 + 1 x 1

= 40 g / mol

Number of moles = Amount of NaOH / Molar mass

= 14.04 /40

= 0.351 mol

So 1000 ml of the solution has 0.351 mol

Molarity of NaOH = 0.351 M

Using the relation

pOH = - log [OH-]

= - log 0.351

= 0.455

Using the relation pH + pOH = 14

pH = 14 - pOH

= 14 - 0.455

= 13.545