Question

Determine the pH of a KOH solution made by mixing 0.251 g KOH with enough water to make 1.0 × 10 2 mL of solution

Answer 1

Answer:

pH = 12.65

Explanation:

From the given information:

number of moles =mass in gram / molar mass

number of moles of KOH = mass of KOH / molar mass of KOH

number of moles of KOH =  0.251 g / 56.1 g/mol = 0.004474 mol

For solution :

number of moles = Concentration × volume

concetration = number of moles/ volume

concetration = 0.004474 mol / 0.100 L

concetration  = 0.04474 M

We know that 1 moles KOH result into 1 mole OH⁻ ions

Therefore,  Molarity  of OH⁻ = 0.04474 M

Now,

pOH = -log[OH⁻]

pOH = -log (0.04474) M

pOH = 1.35

Similarly,

pH + pOH = 14

pH = 14 - pOH

pH = 14 - 1.35

pH = 12.65