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What is buffer solutions ? Explain types of buffer solutions by examples. |
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Answer» Solution :DEFINATION : The solutions which resist change in pH on dilutionor with the addition of small amounts of acid or ALKALI are called Buffer solutions. Buffer solutions are two types like acidic and basic. (A)Acidic buffer solutions : The pH value of this solutions is less than 7.0 . The examples of acidic buffer as under.  pH of a acidic buffer is CALCULATE as following : pH=`pK_a + log "[Salt]"/"[Acid]"`...(Eq.-i) `pH=pK_a + "log" (["Conjugate base" A^-])/"[Acid HA]"`....(Eq.-ii) In it `[H_3O^+]=K_a ([HA])/([A^-])` ....(Eq.-iii) This equation is KNOWN as Henderson Hasselback equation . Here weak acid HA is ionised in less amount. (B) Basic buffer solutions : The pH value of buffer solutions is more than 7.0 is known as basic buffer solution . Basic buffer is formed by mixing of weak base and its salt of strong acid. Examples of basic buffer :  pH of basic buffer is calculate by following : `pH=pK_w`-(`pK_b` + log salt/base) ...(Eq.-i) pH=`pK_a - "log" (["Conjugate acid" BH^+])/"[Base B]"`....(Eq.-ii) pOH=`pK_b+"log" (["Conjugate acid" BH^+])/"[Base B]"` ...(Eq.-iii) `=pK_b+ "log" "[Salt]"/"[Base]"` ...(Eq.-iv) The pH of buffer solution after dilution does not change as the ratio of exponent factor remain unchange. |
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