Buffer solutions (Alkaline) Flashcards Preview

Topic 12.2 (Acid-base titrations) > Buffer solutions (Alkaline) > Flashcards

Flashcards in Buffer solutions (Alkaline) Deck (6)
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the most common example of a weak base and its conjugate acid buffer is

ammonia and the ammonium ion


the ammonium is usually supplied through

ammonium chloride (NH4Cl)


the equilibrium equation showing the balance between the ammonium ion and ammonia is :

NH4+ ⇌ NH3 + H+


the mixture below provides relatively......concentrations of both .....and....
NH4+ ⇌ NH3 + H+

NH4+ ions and NH3


the mixture, NH4+ ⇌ NH3 + H+, will cerate a buffer solution with a pH.........than 7



the NH3 and NH4+ buffer works by:

the addition of acid results in the added H+ reacting with the NH3 to make:
H+ + NH3 → NH4+
the addition of a base leads to the added OH- reacting with the NH4+ ions:
NH4+ + OH- → NH3 + H2O
as there is a relatively high concentraiton of both NH3 and NH4+, the ratio of [NH3] and [NH4+] remains fairly constant when small amounts of either H+ or OH- are added. the means the pH remains relatively constant as

pH = pKa + lg ([NH3] / [NH4+] and as pKa is a constant at a given temperature, the pH of the solution depends on the ratio of [NH3] to [NH4+]