Question

1. Identify the acid, base, conjugate acid and conjugate base in the following reaction: HPO42+ H20 OH H2PO4 2. Calculate the following a) pH of a [H30*] = 2.76 x 104 M b) pH of a [OH] - 8.5 x 10-6 M c) [H30*] and [OH] for a soln pH 5.73 3. Show how an incoming acid [H30*] is neutralized by the buffer system HCO3 /CO32 system. You should also be able to show the neutralization of incoming base [OH'] for this same buffer system.

Answer 1

1) They are identified:

Acid: H2O

Base: HPO4-2

Conjugated acid: H2PO4-

Conjugate Base: OH-

2) a) pH = - log [H3O +] = - log 2.76x10 ^ -4 = 3.56

b) pOH and pH are calculated:

pOH = - log 8.5x10 ^ -6 = 5.07

pH = 14 - 5.07 = 8.93

c) It is calculated:

[H3O +] = 10 ^ pH = 10 ^ -5.73 = 1.86x10 ^ -6 M

[OH-] = 10 ^ -14 / 1.86x10 ^ -6 = 5.38x10 ^ -9 M

3) The ion is neutralized as follows:

H3O + + CO3-2 = HCO3- + H2O

Y

OH- + HCO3- = CO3-2 + H2O

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