BIOL 1406
PreLab 3.4
How do solutions of various pHs compare?
Remember that in a neutral solution, [H+] = 1 x 10-7 M. In addition, an acidic solution has a higher [H+] than a neutral solution, and a basic solution has a lower [H+] than a neutral solution. Remember too, that as the absolute value of a negative exponent gets larger (-1, -2, -3, -4…), the number it represents gets smaller. For example, 1 x 10-7, or 0.0000001 is ten times smaller than 1 x 10-6 or 0.000001.
The following table may help you remember how numbers with different negative exponents compare:
|
Comparing numbers with negative exponents |
||
| Scientific notation | 1 x 10-2 | 1 x 10-1 |
| Decimal | 0.01 | 0.1 |
| Fraction | 1/100 | 1/10 |
| Showing both with a common denominator | 1/100 | 10/100 |
| How many hundredths does each represent? | one | ten |
| Logarithm | - 2 | - 1 |
| - log | 2 | 1 |
| YOUR TURN | |||||
| Fill in the [H+] for each of the following solutions. Make sure your answer includes units. Also make sure that the exponents of your answers use only integer powers (e.g., 10-7 or 10-2). Use a calculator to convert non-integer exponents to integers (e.g. 10-2.6 becomes 2.5 x 10-3.) | |||||
| For pH 5, [H+] = | Hint | Check your answer. | For pH 2, [H+] = | Hint | Check your answer. |
| For pH 9, [H+] = | Hint | Check your answer. | For pH 12, [H+] = | Hint | Check your answer. |
| For pH 6, [H+] = | Hint | Check your answer. | For pH 7, [H+] = | Hint | Check your answer. |
| For pH 3.2, [H+] = | Hint | Check your answer. | For pH 8.7, [H+] = | Hint | Check your answer. |
| YOUR TURN | ||
| Determine which pHs in the previous table are acidic. List the acidic pHs below, in order from most acidic to least acidic. Also fill in the [H+] of each solution. | ||
| Most acidic pH [H+] = | Hint | Check your answer. |
| acidic pH [H+] = | Hint | Check your answer. |
| acidic pH [H+] = | Hint | Check your answer. |
| Least acidic pH [H+] = | Hint | Check your answer. |
| Next, determine which pHs in the previous table are basic. List the basic pHs below, in order from most basic to least basic. Also fill in the [H+] of each solution. | ||
| Most basic pH [H+] = M | Hint | Check your answer. |
| basic pH [H+] = M | Hint | Check your answer. |
| Least basic pH [H+] = M | Hint | Check your answer. |
| How do solutions of different pH compare? | ||
| A solution of pH 5 has a
times larger concentration of H+
than a solution of pH 6.
Therefore a pH 5 solution is times more acidic than a pH 6 solution. |
Hint | Check your answer. |
| A solution of pH 2 has a
times larger concentration of H+
than a solution of pH 6.
Therefore a pH 2 solution is times more acidic than a pH 6 solution. |
Hint | Check your answer. |
| A solution of pH 9 has a
times lower concentration of H+ than
a solution of pH 7.
Therefore a pH 9 solution is times more basic than a pH 7 solution. |
Hint | Check your answer. |
| A solution of pH 12 has a
times lower concentration of H+ than
a solution of pH 9.
Therefore a pH 12 solution is times more basic than a pH 9 solution. |
Hint | Check your answer. |
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