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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1

the most common example of a weak base and its conjugate acid buffer is

ammonia and the ammonium ion

2

the ammonium is usually supplied through

ammonium chloride (NH4Cl)

3

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

NH4+ ⇌ NH3 + H+

4

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

NH4+ ions and NH3

5

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

greater

6

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+]