Question

It has been found that the pH of a 0.01 M solution of an organic acid is 4.15. Calculate the concentration of the anion, the ionisation constant of the acid and its pKa.

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Solution

pH equals 4.15 comma space straight c equals 0.01 straight M pH equals negative log left square bracket straight H to the power of plus right square bracket equals 4.15 left square bracket straight H to the power of plus right square bracket equals antilog left parenthesis negative 4.15 right parenthesis equals 7.08 straight x 10 to the power of negative 5 end exponent space straight M left square bracket straight H to the power of plus right square bracket equals space cα space equals 7.08 space straight x space 10 to the power of negative 5 end exponent space straight M equals square root of cK subscript straight alpha space end root space equals square root of 0.01 straight K subscript straight alpha end root Concentration space of space anion colon left square bracket straight A to the power of minus right square bracket equals left square bracket straight H to the power of plus right square bracket space equals 7.08 space straight x 10 to the power of negative 5 end exponent space straight M Ionisation space constant space of space the space acid colon left square bracket straight H to the power of plus right square bracket space equals square root of 0.01 end root straight K subscript straight alpha space equals 7.08 space straight x 10 to the power of negative 5 end exponent 0.01 straight K subscript straight alpha space equals left parenthesis 7.08 space straight x 10 to the power of negative 5 end exponent right parenthesis squared straight K subscript straight alpha equals fraction numerator left parenthesis 7.08 space straight x 10 to the power of negative 5 end exponent right parenthesis squared over denominator 0.01 end fraction space equals 5.01 space straight x 10 to the power of negative 7 end exponent pK subscript straight a space equals negative logK subscript straight a space equals negative log space 5.01 space straight x 10 to the power of negative 7 end exponent space equals 6.3

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Equilibrium

It has been found that the pH of a 0.01 M solution of an organic acid is 4.15. Calculate the concentration of the anion, the ionisation constant of the acid and its pKa.

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?

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