Question

Comment on the statement: Strong acid has a weak conjugate base and vice-versa.

Solution

According to Bronsted Lowry concept:
(i) the strength of an acid depends on upon its tendency to donate proton and
(ii) the strength of base depends on upon its tendency to accept a proton.
Consider a reaction between HNO₃ and water.
$stack HNO subscript 3 with Strong space acid below space plus space stack straight H subscript 2 straight O with Strong space base space below space space space space leftwards harpoon over rightwards harpoon space space space space space space stack straight H subscript 3 straight O to the power of plus with Weak space acid below space space space plus space stack NO subscript 3 superscript minus with Weak space base below$
HNO₃ has a greater tendency to donate a proton than H₃O⁺ ion. Therefore. HNO₃ is a strong acid, NO₃^– ion has a very little tendency to accept a proton, therefore, NO₃^– ion is a weak base.
$Strong space acid space space space rightwards harpoon over leftwards harpoon space space space straight H to the power of plus space plus space Weak space conjugate space base.$
Thus strong acid has a weak conjugate base.
Now consider the reaction between acetic acid and water.
$stack CH subscript 3 COOH with Weak space acid below space plus space stack straight H subscript 2 straight O with Weak space base below space space space leftwards harpoon over rightwards harpoon space space space stack straight H subscript 3 straight O to the power of plus with Strong space acid below space plus space space stack CH subscript 3 COO to the power of minus with Strong space base below$
Acetic acid has a small tendency to donate a proton, therefore, it is a weak acid. CH₃COO^–ion has strong tendency to accept a proton, therefore, CH₃COO^– ion is a strong base.
$Weak space acid space space space rightwards harpoon over leftwards harpoon space space space straight H to the power of plus space plus space Strong space conjugate space base$
Thus weak acid has a strong conjugate base.

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Equilibrium

Comment on the statement: Strong acid has a weak conjugate base and vice-versa.

Some More Questions From Equilibrium Chapter

Which measurable property becomes constant in water vapour equilibrium?

Give an example from daily life in which there is gas solution equilibrium?

A crystal of common salt of a given mass is kept in its aqueous solution. After 24 hours, its mass remains the same. Is the crystal in equilibrium with the solution?

What is the role of forward and backward reactions at equilibrium of a reversible reaction?

What is a forward reaction?

What condition favours a reversible reaction?

What is a backward reaction?

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