Answer:
2.58
Explanation:
Each tablet has a mass of 470 mg. The mass of 2 tablets is 2 × 470 mg = 940 mg = 0.940 g
The molarity of acetylsalicylic acid (aa) is:
M = mass of aa / molar mass of aa × liters of solution
M = 0.940 g / 180.16 g/mol × 0.240 L
M = 0.0217 M
Acetylsalicylic acid is a weak acid, so we can find [H⁺] using the following expression.
[H⁺] = √(Ca × Ka)
where,
Ca: concentration of the acid
Ka: acid dissociation constant
[H⁺] = √(0.0217 × 3.24 × 10⁻⁴)
[H⁺] = 2.65 × 10⁻³ M
The pH is:
pH = -log [H⁺] = -log 2.65 × 10⁻³ = 2.58
