Further introduction to the concept of pH

 Hello, yesterday, we started off looking at the meaning of the term pH in chemistry and we agreed that the pH is defined as the negative logarithm of the hydrogen ion concentration. In modern chemistry, the p stands for "the negative decimal(base ten) logarithm of". Previously we saw that pKa means the negative logarithm of the acid dissociation constant. Also, pKb means the negative logarithm of the base dissociation constant. Do you now see that our definition of the term “p” in chemistry holds true always?


Closely related to the pH is another term called the pOH. The pOH is the negative logarithm of the hydroxide ion concentration. Thus, while pH and pKa applies to acids, pOH and pKb applies to bases. Is that making sense?


Without much ado, we have to bear in mind that the pH tells us how acidic a substance is. It is the indicator of the degree of acidity or alkalinity (basicity) of a substance. Generally, the pH of substances can be arranged in a scale of 1 – 14 and this is called the pH scale. 


pH 1 – 4 means very acidic

pH 5 – 6.9 means mildly acidic

pH 7 Means neutral

pH 8 – 10 means mildly basic

pH 11- 14 means very basic


Let me drop this here because we shall soon be applying the concept. It is known in chemistry that pH + pOH = 14. In the next few days, we shall focus our attention on mathematical examples that involves these concepts.


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