Titration curve for an Consider the attached graph of a weak diprotic acid. A 0.

Question

Titration curve for an Consider the attached graph of a weak diprotic acid. A 0.2658 g sample titrated with 0.1000 M NaOH. Based on the data complete the following: ml of NaOH used to reach the first endpoint Mols of the acid present in the sample Consider malonic acid, a typical diprotic weak acid: H-O-C-CH_2-C-O-H. If 1 mol of the acid is dissolved in water and 0.5 mol of sodium hydroxide is added: How much of the malonic acid left in the solution? The sodium hydroxide reacts with the malonic acid to form what chemical species (show any charges) along with water. What is the relationship between malonic acid and the species from B)? When mols of a weak acid in solution are equal to mols of its conjugate the pH of the solution is equal to the of the weak acid

Explanation / Answer

consider 1 mol of acid dissolved in 1000ml of water and also to which the 0.5 mol of base is added , thus the concentarion of acid = 1 M

and conc of base added = 0.5 M

since only 1 proton will come aout to react with the base added

thus concentration of acid = 0.5M

B)

CH2(COOH)2 + NaOH ----> NaOOC-CH2-COOH + H2O

(species B)

C)

species B is the conjugate base of malonic acid

D) moles of acid = moles of conjugate base = 0.5 M

thus pH = pKa + log([salt] / [base])

thus

pH = pKa = 2.83 (pKa pf malonic acid = 2.83)

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