SCH 3U/4C - pH Scale & Acid Rain

pH Scale

Recall that the pH scale typically runs from 0 to 14 (although it is possible to have a pH outside that range).  The pink region is acidic (stomach acid, lemon juice, vinegar, battery acid), the purple neutral (pure water, saline solution) and the blue is basic (antacids, baking soda, bleach, drain cleaner).

0     1     2     3     4     5     6     7     8     9    10    11    12    13    14

The [H⁺] in solution is usually quite small, ∴ we usually express [H⁺] in terms of pH.  A change in one unit of pH, changes the concentration tenfold.  You should recall this equation from grade 10 science:

pH = -log[H⁺]

ex. If [H⁺] = 1.0 x 10^-7 M, what is the pH of the solution?   

pH = -log [H⁺]
pH = -log(1.0 x 10^-7) 

      = 7.00*

ex. A sample of apple juice has a pH of 3.76.  Calculate the hydrogen ion concentration.

      pH = -log [H⁺]

    3.76 = -log[H⁺]

log[H⁺] = -3.76      

(To remove the log, take the anti-log - it's the 10^x button on your calculator - usually found as the second function on the log button.)

     [H⁺] = 10^-3.76

     [H⁺] = 1.74 x 10^-4 M*

*Tip:  There are specific rules for rounding when using log.  However, let's make life simpler and just use two decimal places, whether reporting a pH value or [H⁺] value in scientific notation.

pH Scale Homework:

Acid Rain Homework:

This reading is from a pamphlet, so the order to read it is a bit odd.  Read the section between the arrows on the first page.  As for the second and third pages, they were originally like a centrefold.  So, read across the top of the second page, then the top of the third page, then the bottom of the second page and finally the bottom of the third page.  Whew!!

I encourage you to answer in point form.  Conversely, you could print out the reading pages and then highlight and indicate the location for each answer.

pH Scale Answers: