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Monday, 17 November 2014

Topic 8.4: The pH scale

8.4.1 Distinguish between aqueous solutions that are acidic, neutral or alkaline using the pH scale

The pH scale is created through this equation

On the pH scale, 7 is neutral, Anything below 7 is acidic and anything above 7 is alkaline.


8.4.2 Identify which of two or more aqueous solutions is more acidic or alkaline using pH values

To identify which of two solution is more acidic or alkaline, we have to understand that the lower the pH value, the more acidic it is. The high the pH value, the more alkaline it is.



8.4.3 State that each change of one pH unit represents a 10-fold change in the hydrogen ion concentration [H+(aq)]

A change of one pH unit represents a 10-fold change in the concentration of hydrogen ions.

This means that increasing the pH by one unit represents a decrease in the concentration of hydrogen by 10 times; decreasing by one pH unit represents an increase in the concentration of hydrogen by 10 times.



8.4.4 Deduce changes in [H+(aq)] when the pH of a solution changes by more than one pH unit

If the pH of a solution is changed from 3 to 5, deduce how the hydrogen ion concentration changes.

pH = 3, so the concentration of hydrogen is 10^-3 mol dm^-3

pH = 5, so the concentration of hydrogen is 10^-5 mol dm^-5

Therefore the concentration of hydrogen has decreased by 100.


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