Question

An environmental scientist needs to use solid NaOH reduce the acidity of a threatened small lake with a volume of 3.00x10^8 L and pH of 4.8 assuming solid NaOH dissociates what mass of NaOH is needed to get the lake from a pH of 4.8 to 6.5?

Answer 1

P^H = 4.8 .

Concentration of H⁺ = 10^-4.8 M.

Concentration Of H⁺ = 1.6 × 10^-5 M.

So, Concentration Of OH^- = 10^-14 / 1.6 × 10^-5 .

Concentration of OH^- = 6.25 × 10^-10 M.

When P^H = 6.5 .

Concentration of H⁺ = 3.2 × 10^-7 M.

Concentration of OH^- = 10^-14 / 3.2 × 10^-7.

Concentration of OH^- = 3.125 × 10^-8. M.

So, moles of NaOH required =

(3.12 × 10^-8 × 3 × 10⁸ - 6.25 × 10^-10 × 3 × 10⁸).

Moles of NaOH Required=

(3.12×3 - 6.25×3×10^-2).mole.

Moles of NaOH = (9.36 - 0.1875) mole.

= 9.1725 moles.

Mass of NaOH = (9.1725 × 40 ). gm.

Mass Of NaOH = 366.9 gm. Answer.