"Practice pH" answers

Here are the answers (and some other thoughts) to the worksheet on pH calculations: 1. [H+] = 2.5 x 10-6 M while [OH-] = 4.0 x 10-9 M. There are two ways of figuring out [OH-]... first, convert pH to pOH and proceed or second way, use [H+] and Kw to get it. Try both ways and become an expert! Note: Rain water is naturally acidic due to various gases in the air (like CO2) that become weak acids when hydrated in clouds. (Recall: Dry ice (CO2) becomes carbonic acid (H2CO3) when bubbled through water :-). "Acid Rain" is when pH is lower than about 5.0 or 4.7. This happens when moisture in the air reacts with specific gases like SO2 and NO2 to form Strong acids (sulfuric and nitric). SO2 is produced when burning coal in many of our nation's power plants and is of real concern in producing Acid Rain. 2. pH = 14.8. Strong base!! Yes, you can have pH greater than 14 and even less than zero (negative!). The pH scale extends in both directions. For this question, there are two ways to get pH from [OH-]... first, take pOH and subtract from 14, or second way, get [H+] with Kw and take pH. Which way do you prefer??