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Equilibrium

Question
CBSEENCH11006555
Wired Faculty App

Calculate the pH of a 0·08M solution of hypochlorous acid, HOCl. The ionisation constant of the acid is 2·5 × 10–5. Determine the percent dissociation of HOCl. 

Solution
Let the amount of HOCl dissociated be x mol L-1
HOCl   +   H2O     rightwards harpoon over leftwards harpoon      H3O+  + ClO- 
Initial conc.      
 0.08                              0          0
At eqm.              
008 - x                          x           x
                    
therefore space space space straight K subscript straight a space equals space fraction numerator open square brackets straight H subscript 3 straight O to the power of plus close square brackets space open square brackets ClO to the power of minus close square brackets over denominator open square brackets HOCl close square brackets end fraction space equals space fraction numerator straight x space cross times space straight x over denominator 0.08 end fraction space equals space fraction numerator straight x squared over denominator 0.08 end fraction space or space space space straight x squared space space equals straight K subscript straight a space cross times space 0.08 space equals space 2.15 space cross times space 10 to the power of negative 5 end exponent space cross times space 0.08 space space space space space space space space space space space space equals space 2.0 space cross times space 10 to the power of negative 6 end exponent or space space space space straight x space equals space square root of 2.0 space cross times space 10 to the power of negative 6 end exponent end root space equals space 1.41 space cross times space 10 to the power of negative 3 end exponent or space space space space open vertical bar straight H subscript 3 straight O to the power of plus close vertical bar space equals space 1.41 space cross times space 10 to the power of negative 3 end exponent straight M space space space pH space equals space minus log space open square brackets straight H subscript 3 straight O to the power of plus close square brackets space equals space minus log space left parenthesis 1.41 space cross times space 10 to the power of minus right parenthesis space space space space space space space space equals space 2.85
percent sign space age space dissociation space equals space fraction numerator Amount space dissociated over denominator Amount space taken end fraction cross times space 100 space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals fraction numerator 1.41 space cross times space 10 to the power of negative 3 end exponent over denominator 0.08 end fraction cross times 100 space equals space 1.76 percent sign

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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