2.3.2

pH

Why do we care about the [H^{+}] anyway? What is special about this particular ion? Well, it turns out that either too much or too little H^{+} can cause serious problems to chemical reactions. We use the terms acidic and basic to describe these conditions. If the [H^{+}] of the solution is greater than 1.0 x 10^{-7}, we say the solution is **acidic**, and if the [H^{+}] is less than 1.0 X 10^{-7}, we say the solution is **basic**.

Because the [H^{+}] is so important and because it is rather cumbersome to say things like, “the [H^{+}] of the fluid is 1.0 X 10^{-7} Molar,” chemists have developed a shorthand to express the [H^{+}]. This shorthand expresses the [H^{+}] as the **pH **of the solution. The pH of a solution is the **negative logarithm of the [H ^{+}] **(concentration expressed as moles per liter, M). So, if the [H

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So, there are two important lessons from this; the lower the pH, the higher the [H^{+}], and a change in pH of one unit (7 to 6 for example) is a 10-fold change in [H^{+}].

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