1.

100 mL of pH = 6 (acidic) is diluted to 1000 mL by H2O. pH will increase approximately by:(a) 9 unit (b) 1 unit(c) 0.7 unit (d) –0.7 unit

Answer»

Correct option: (c) 0.7

Explanation: 

On dilution,

N1V1 = N2V2

10–6 x 100 = N2 x 1000

N2 = 10–7 N

Since acid solution has pH < 7, it will remain acidic even after dilution,

Hence, total [H+] = [H+]acid + [H+]water

= 10–7 + 10–7 = 2 x 10–7 N

∴ pH = – log [H+] = – log (2 x 10–7) = 7 – log 2

= 6.7

Thus, change in pH = 0.7 unit



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