27. 2 H20() H3O+(aq) + OH-(aq) The autoionization of water is represented by the

Question

27. 2 H20() H3O+(aq) + OH-(aq) The autoionization of water is represented by the equation above. Values of pKw at various temperatures are listed in the table below. Temperature (C 0 10 25 30 40 14.9 14.5 14.0 13.8 13.5 Based on the information above, which of the following statements is true? (A) The pH of neutral water at 30°C is 7.00. (B) The pH ofpure water is greater than the pOH of water above 25°C. (C) The pH of pure water is greater than the pOH of water below 25°C. (D) The pH of pure water is equal to the pOH at 0°C.

Explanation / Answer

Option A is wrong as pH at 30oC is half of that of pKw 13.8/2= 6.9

Option B is also wrong answer because above 25oC dissocation of water increses which lowers the pH making water more acidic

option C  isr ight answer because below 25 oC,water dissocation is lowered which increses ionic product of water,thus increasing pH of water like from 7 to 7.45 at 0 oC and 7.25 at 10 oC.

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