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PLEASE EXPLAIN HO CAN WE COMPARE STRENGTH OF BASES USING BRONSTED LOWRY THEORY?

PLEASE EXPLAIN HO CAN WE COMPARE STRENGTH OF BASES USING BRONSTED LOWRY THEORY?

Grade:9

1 Answers

Saurabh Kumar
askIITians Faculty 2400 Points
8 years ago
The acid dissociation constant of the Bronsted-Lowry acid (Ka) is the quantity which is actually used to measure the strength of the acid quantitatively (rather than the equilbrium constant itself). This is simply the product of the hydronium ion concentration and the concentration of the conjugate base of the acid (both on the product side of the equilibrium), divided by the concentration of the Bronsted acid itself(on the left hand side of the equation). Notice that the concentration of water, which is also on the left hand side of the equation, is omitted from the expression, since this is effectively constant in dilute aqueous solution. Thus the acid dissociation constant is the equilibrium constant K multiplied by the constant concentration of water in water.



Frequently, the pKa, which is the negative common log of the acid dissociation constant is used as a more conveniently-sized number to measure the acidity. Since this is the negative log, a large positive pKa means a large negative exponent of the acid dissociation constant, Ka. this corresponds to a weak acid (Ka greater than 1 indicates more product than reactant; Ka less than 1 indicates more reactant than product; the hydronium ion is on the product side). Conversely, a negative value of the pKa corresponds to a strong acid.

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