chemistry

what will be the pH change when 20 mL of .1M NaOH is added to 80 mL of a buffer solution consisting of .164M NH3 and .187M NH4Cl? Pka 9.25

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  1. Use the Henderson-Hasselbalch equation to obtain the initial pH. I have something like 9.19 but you need to confirm that and do it more accurately than I estimated.
    Then work the addition part of the problem.
    You started with 80 mL x 0.187 M NH4Cl = 13.12 mmoles.
    You started with 80 mL x 0.164 = 14.96 mmoles. Now we add NaOH and I like to use an ICE chart.
    ........NH4^+ + OH^- ==> NH3 + H2O
    initial 14.96....0......13.12......
    change..-2.....+2mmoles..+2
    final...12.96....0......15.12

    Now substitute into the HH equation and solve for the new pH. I think 9.3 is close for the new pH.

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    posted by DrBob222

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