$pH$ of buffers

Tutorial 3

         

Calculating the pH of a buffer Buffer definition: A buffer is a mixture of a weak base with its conjugated acid pH calculation: In the following calculation only the numbers of moles or molarities before dissociation or before interaction between the species present are included! $ pH $ $ = $ $ pK_a \; + \; \frac{n_{base}} {n_{acid}} $ $ pH $ $ = $ $ pK_a \; + \; \frac{c_{base}} {c_{acid}} $ where $ n $ are the numbers of moles $ c $ the molarities taking into account the dilution during mixing

To a mixture of $2\;L\;0.1M\;CH_3COOH$ with $1\;L\;0.2M\;CH_3COONa$ we add $3\;L$ of water. What is then the pH ? First the number of moles!

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