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Unformatted text preview: alkaline and pH > 7. Thus, the acidity or basicity of an aqueous
solution can be determined from its pH. Equation 4
pH = - log[H3O+]
can be solved for the hydronium ion concentration to obtain equation 5
[H3O+] = 10-p H
www.webassig n.net/ebooks/wsug encheml1/lab_11/manual.html 2/5 4/15/13 Lab 11 - Acid- Base Studies .
[H3O+] = 10-p H
Thus, a pH of 2.2 implies that [H3O+] = 10-p H = 10-2.2 = 0.006 M.
The acidity or basicity of a solution
can be determined by measuring its pH or with an indicator. pH meters are electrochemical cells whose voltage
is pH sensitive. When the electrode from the meter is placed in a solution, a voltage is developed between the
meter and the solution. The voltage is converted to a pH that can be read directly. An acid- base indicator is a
weak acid whose conjugate base is a different color. When the indicator is placed in an acidic solution, it is
converted to the acid form and takes that color, but when it is placed in a basic solution, it is converted to the
base and takes on the color of the base.
pH paper is a strip of paper with an indicator on it. The color of the
indicator changes with pH, so the approximate pH of a solution can be determined by placing a small amount of
the solution on the paper. In Part A of this lab, you will use pH meters to determine the pH of several acidbase solutions commonly found in a chemistry laboratory to become familiar with the pH scale. In Part B, you
will use pH paper to determine whether several common household chemicals are acidic, basic, or neutral. In
Part C, you will use a pH meter to follow the pH change of an acidic solution as a basic solution is added to it. Equipment
1 30 mL beaker
1 10 mL graduated cylinder
1 glass stir rod
7 medium test tubes
1 test tube rack
1 pH meter
1 pH paper
1 plastic work surface
1 deionized water squirt bottle R...
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