O F A C I D S A N D B A S E S

 Logarithms: the common logarithm of a number is the exponent to which ten must be raised to produce the given number: Log x = y, if x = 10 y .
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So…. Log 0.01 = -2; because 0.01 = 10 -2
And log 10,000 = 4; because 10,000 = 10 4

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The antilog of a number x is the number y whose logarithm is x. Because log y = x means y=10 x , the antilog of x is the same as 10 x
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In calculator….2
nd function log (pH value) enter
Write your answer in scientific notation
Use this to calculate molarity when given pH
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Example: pH = 7.0
Antilog (7.0) = 10,000,000
Molarity) = 1.0 x 10 7

 To calculate the pH of substance:
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 pH = -log [H + ]
For H + use the molarity concentration given
 When calculating pH of a base, you must FIRST use the constant value of 1 x 10 -14 and divide it by the given molarity of OH – THEN use the log formula above

 When given pH and asked to solve for molarity you will likely need to use the logarithm table in your textbook; especially if the pH is a decimal number
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Example: pH is 3.70
To do this: FIRST rearrange the given information so that you have a negative pH
-pH = -3.70

 Next: add and then subtract the whole number that is closer to and larger than the negative pH value
(that number would be 4)
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= (-3.70 + 4) – 4
= 0.30 – 4
= 10 (0.30 -4)
= 10 0.30
x 10 -4
From the log table, find the number with a log of
0.30 (it’s 2.0); the antilog of 0.30 is thus 2.0

 From the log table, find the number with a log of
0.30 (it’s 2.0); the antilog of 0.30 is thus 2.0
 So……………….. 2.0 x ?
 The number with a log of -4 is 10 -4
 Therefore, [H+] = 2.0 x 10 -4 M

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Complete calculations
SHOW ALL EQUATIONS you set up
Circle your final answers WITH units*
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Textbook: page 586 – 589
Problems # 8 - # 15
*Remember concentration has the unit of measure
Molarity (M); pH does not have a unit