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Equilibrium

Question
CBSEENCH11006496
Wired Faculty App

Calculate the degree of ionisation and hydronium ion concentration of a 0·02 M acetic acid at 298K. The dissociation constant of acid is 1·8 × 10–5 at 298K.

Solution
Let a be the degree of dissociation of the acetic acid.
CH3COOH     rightwards harpoon over leftwards harpoon with Water on top    CH3COO-(aq) + H3O+
Initial conc.
       C                     0                   0
Equilibrium
 straight C minus Cα                    Cα                Cα
Applying law of chemical equilibrium,
   
 straight K subscript straight a space equals space fraction numerator open square brackets CH subscript 3 COO to the power of minus left parenthesis aq right parenthesis close square brackets space open square brackets straight H subscript 3 straight O to the power of plus close square brackets over denominator open square brackets CH subscript 3 COOH close square brackets end fraction or space space space space space space space space space straight K subscript straight a space equals space fraction numerator Cα space cross times space Cα over denominator straight C minus Cα end fraction space equals space fraction numerator straight C squared straight alpha squared over denominator straight C left parenthesis 1 minus straight alpha right parenthesis end fraction equals space fraction numerator Cα squared over denominator 1 minus straight alpha end fraction or space space space space space space space straight K subscript straight a space equals space Cα to the power of 2 space space space space end exponent space space space space space space space space space space space space space space space space space space space space space open square brackets because space space space 1 space minus space straight alpha space equals space 1 close square brackets or space space space space space space space space straight alpha squared space equals space straight K subscript straight a over straight C space equals space fraction numerator 1.8 space cross times space 10 to the power of negative 5 end exponent over denominator 0.02 end fraction space equals space 9 space cross times space 10 to the power of negative 4 end exponent or space space space space space space space space straight alpha space equals space 3 space cross times space 10 to the power of negative 2 end exponent But space space open square brackets straight H subscript 3 straight O to the power of plus close square brackets space equals space Cα space equals space 0.02 space cross times space 3 space cross times space 10 to the power of negative 2 end exponent space space space space space space space space space space space space space space space space space space equals space 6 space cross times space 10 to the power of 4 space mol space straight L to the power of negative 1 end exponent space space space space space space space space space

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?

What type of equilibrium is attained in a reversibe chemical change?

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