pH, Acid-Base, Indicators,

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Experiment 9 - pH, Acid-Base Indicators, Buffers

Postlab Questions:

  1. Explain the differences in the pH of the following solutions:
    (a) 0.1 M HCl and 0.1 M CH3COOH
    (b) 0.1 M NaOH and 0.1 M NH4OH

  2. Suppose you tested 3 samples of an unknown solution "X", with each of the three indicators used in this experiment and you obtained the following results:
    (i) on adding methyl orange, the solution is yellow
    (ii) on adding bromothymol blue, the solution is yellow
    (iii) on adding phenolphthalein, the solution is colourless

    Using the information you obtained with regard to the pH at which these indicators change colour, deduce the pH of the unknown solution "X".

  3. How does the pH of a buffer solution change when acid or base is added to it compared with when the acid or base is added to distilled water?



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