Calculate the pH of a 1. 02 times 10-2 M solution of the decongestant ephedrine

Question

Calculate the pH of a 1. 02 times 10-2 M solution of the decongestant ephedrine hydrochloride if the pKb, of ephedrine (its conjugate base) is 3. 86. A 25. 0-mL sample of a 0. 260 M solution of aqueous trime thylamine is titrated with a 0. 325 M solution of HCI. Calculate the pH of the solution after 10. 0, 20. 0. and 30. 0 mL of acid have been added; pKb, of (CH3)3N = 4. 19 at 25degree C. What is the pH at the equivalence point when 75. 00 mL of a 0. 175 M solution of acetic acid (CH3COOH) is titrated with 0. 10 M NaOH to its end point?

Explanation / Answer

similar problem , please do solve.

3)What is the pH at the equivalence point in the titration of 10.0mL of 0.32 M CH3CO2H with 15.0mL of 0.213 M NaOH? For CH3COO-, Kb=5.6*10^-10?

at the equivalence point moles of NaOH added equals moles of acetic acid present
n NaOH = n CH3CO2H = M*V = 0.213*0.015= 3.20*10^-3 mol = n CH3COO- formed
final solution volume = 25.0 mL = 2.5*10^-2 L
[CH3COO-] = n/V = 3.20*10^-3 / 2.5*10^-2 = 0.128 M
acetate is basic
[OH-] = square root(5.6*10^-10*0.128) = 8.47*10^-6 M
pH = 8.93

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