Define Bransted-Lowry acids and bases. Differentiate between the dissociation co

Question

Define Bransted-Lowry acids and bases. Differentiate between the dissociation constant and equilibrium constant for the dissociation of a weak acid, HA, in aqueous solution. Why isn't the pH at the equivalence point always equal to 7 in a neutralization titration? When is it 7? What is the pK_a of an acid whose K_a is 6.5 times 10^-6 Why must two electrodes be used to make an electrical measurement such as pH? What is a buffer solution? The pH at one half the equivalence point in an acid-base titration was found to be 6.57. What is the value of Ka for this unknown acid? If 30.15 mL of 0.0995 M NaOH is required to neutralize 0.279 g of an unknown acid, HA, what is the molecular weight of the unknown acid? If K_a is 1.85 times 10^-5 for acetic acid, calculate the pH at one half the equivalence point and at the equivalence point for a titration of 50 mL of 0.100 M acetic add with 0.100 M NaOH.

Explanation / Answer

1 ) according to bronsted -lowry :

an acid is substance which gives H+ ion , and base is substance which accept H+ ion

2)
dissociation constant is for any compound that is for may be weak acid , weak base of weak salt or any compound

suppose an electrolyte AB

AB <--------------> A+ + B-

K = [A+][B-]/[AB]

if AB is weak acid dissociation constant will be Ka .

3)

in case weak acid Vs strong base titration pH > 7 at equivalence point because base is dominent

in case weak base Vs strong acid titration pH < 7 at equivalence point because acid is dominent

if both are strong pH = 7.

4)

Ka = 6.5 x 10^-6

pKa = -log (6.5 x 10^-6)

pKa = 5.19

6 )

buffer solution whose pH does not change on addition of small amount of an acid or base

or

a solution which resist to change in its pH is known as buffer solution

example : weak acid + its conjugate base

                CH3COOH + CH3COO-

                HCN + CN-

              H3PO4 + H2PO4-

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