# The active ingredient in aspirin is acetylsalicylic acid. A 2.19 g sample of acetylsalicylic acid required 23.53 mL of 0.5167 M NaOH for a complete reaction. The addition of 13.81 mL of 0.4402 M HCl to the flask containing the aspirin and the sodium hydroxide produced a mixture with pH = 3.48. Find the molar mass (in g/mol) of acetylsalicylic acid and its Ka value. Acetylsalicylic acid is a monoprotic acid.

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The active ingredient in aspirin is acetylsalicylic acid. A 2.19 g sample of acetylsalicylic acid required 23.53 mL of 0.5167 M NaOH for a complete reaction. The addition of 13.81 mL of 0.4402 M HCl to the flask containing the aspirin and the sodium hydroxide produced a mixture with pH = 3.48. Find the molar mass (in g/mol) of acetylsalicylic acid and its Ka value. Acetylsalicylic acid is a monoprotic acid.

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Step 1

The number of moles of acetylic salicylic acid and sodium hydroxide reacted are equal because acetylsalicylic acid is monoprotic and complete neutralization reaction takes place. Let the molar mass of acetylsalicylic acid is x g/mol. The number of moles of acetylic salicylic acid and sodium hydroxide is calculated using the equation below.

Step 2

The molar mass of acetylsalicylic acid is calculated by equating the moles of acetylic salicylic acid and sodium hydroxide:

Step 3

The number of moles of acetylsalicylate formed is 0.012 mole. When hydrochloric acid will be added to formed sodium acetylsalicylate it will convert bac...

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