Chemistry Qbank 2 #23

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Joined: Fri May 25, 2018 9:15 am

Chemistry Qbank 2 #23

Postby NS_Tutor_Will » Thu Aug 16, 2018 12:21 pm

A student stated about this question: "pOH and pH are reciprocals. Therefore, if pH decreases, pOH must increase."

pH + POH = 14 holds true only at 25°C. In this question, the temperature has increased, so that relationship no longer holds true. The autoionization of water, we are told, is an endothermic process. Because it is endothermic, the reaction (2 H2O <--> H3O+ + OH-) will shift to the right when the temperature increases. As a result, both the H+ concentration and the OH- concentration will increase. Thus, because it is a negative log, the pH and pOH will both decrease.

Good luck!

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