Buffer solutions (Alkaline)

Question 1

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

Answer 1

ammonia and the ammonium ion

Question 2

the ammonium is usually supplied through

Answer 2

ammonium chloride (NH4Cl)

Question 3

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

Answer 3

NH4+ ⇌ NH3 + H+

Question 4

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

Answer 4

NH4+ ions and NH3

Question 5

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

Answer 5

greater

Question 6

the NH3 and NH4+ buffer works by:

Answer 6

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+]