The active ingredient in aspirin is acetylsalicylic acid (hc9h7o4), a monoprotic acid with a ka of 3.3×10−4 at 25 ∘c . you may want to reference (pages 680 - 690) section 16.6 while completing this problem. what is the ph of a solution obtained by dissolving two extra-strength aspirin tablets, containing 440 mg of acetylsalicylic acid each, in 270 ml of water? express your answer to two decimal places.

pH = 2.76

Explanation:

Given that:

Given that:

Mass = 440 mg = 0.44 g (1 mg = 0.001 g)

Molar mass = 180.158 g/mol

The formula for the calculation of moles is shown below:

Thus,

Given Volume = 270 mL = 0.27 L ( 1 mL = 0.001 L)

Concentration = 0.00904 M

Consider the ICE take for the dissociation of acetic acid as:

                                   HC₉H₇O₄    ⇄     H⁺ +     C₉H₇O₄⁻

At t=0                          0.00904                 -              -

At t =equilibrium      (0.00904-x)                x           x            

The expression for dissociation constant of acetic acid is:

x is very small, so (0.00904 - x) ≅ 0.00904

Solving for x, we get:

x = 1.7272×10⁻³  M

pH = -log[H⁺] = -log(1.7272×10⁻³) = 2.76