A buffer is a solution that resists changes to its pH. It is comprised of: A str
ID: 1049057 • Letter: A
Question
A buffer is a solution that resists changes to its pH. It is comprised of: A strong acid and a strong base. A strong acid and a neutral salt. A weak base and an amphoteric compound A weak acid and its conjugate base The picture below depicts a titration of a weak acid with dilute NaOH: Which of the following best describes the acid? It is a diprotic acid It is a triprotic acid It is a strong acid It is a concentrated solution An acid, HA, has a dissociation constant of 1.75 times 10^+. What is the pH of a 1.00 M solution of HA? 1.00 5.76 6.00 8.38 Which of the following mixtures would NOT produce a buffer? Formic acid and sodium formate Ammonia and ammonium chloride Malic acid and sodium malate Hydrochloric acid and silver nitrateExplanation / Answer
4) A buffer is made from either
i) a weak acid and its conjugate base
or ii) a weak base and its conjugate acid
as the conjugate acid/base of weak base/ acid undergoes hydrolysis.
5) It is a di basic acid as you can see at two places a pH jump. Each pH jump corresponds to one H+ being neutralised.
6) pH of a weak acid is given by
pH = 1/2 pKa -1/2 log C
Given Ka = 1.75 x 10-6 and C = 1.0M
Thus pH =1/2[ 6 - log 1.75] - 1/2 log 1.0
= 2.878
None of the given options seem to be correct.[probably it should have been a buffer with some NaA added]
7) A) formic acid and formate form a buffer as they are weak acid and its conjugate base.
B0) Ammonia is weak base and its conjugate acid is ammonium (chloride) . hence it is a buffer
C) Malic acid is also a weak acid and solution has malate, its conjugate base. thus a buffer
D) HCl is astrong acid and the solution does not have its conjugate base also. so NOT a buffer.
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