Q30Short answer
pH of a solution of a strong acid is 5.0. What will be the pH of the solution obtained after diluting the given solution a 100 times?
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(i) pH = 5 + –5 –1 [H ] = 10 mol L On 100 times dilution + –7 –1 [H ] = 10 mol L + On calculating the pH using the equation pH = – log [H ], value of pH comes out to be 7. It is not possible. This indicates that solution is very dilute. Hence, Total hydrogen = [H+] ion concentration ⎡Contribution of ⎤ ⎡Contribution of ⎤ ⎢H O+ ion ⎥ ⎢H O+ ion ⎥ = ⎢concentration ⎥ 3 + ⎢concentration ⎥ ⎢of acid ⎥ ⎢of water ⎥ ⎣ ⎦ ⎣ ⎦ –7 –7 = 10 + 10 . pH = 2 × 10–7 = 7 – log 2 = 7 – 0.3010 = 6.6990 BaSO4 (s) 2–