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Changes in pH in the absence of a buffer

Changes in pH in the absence of a buffer. What happens when 1 mL of 1.0 M HCl is added to 99 mL of water at pH 7.0 ?. Changes in pH in the absence of a buffer. Changes in pH in the absence of a buffer. Changes in pH in buffer. In a 100 mL of 1.0 M histidine solution at pH 6.6

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Changes in pH in the absence of a buffer

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  1. Changes in pHin the absence of a buffer • What happens when 1 mL of 1.0 M HCl is added • to 99 mL of water at pH 7.0 ?

  2. Changes in pHin the absence of a buffer

  3. Changes in pHin the absence of a buffer

  4. Changes in pHin buffer In a 100 mL of 1.0 M histidine solution at pH 6.6 60 mL of 1.0 M HCl is added What is the final pH of the solution?

  5. Changes in pHin buffer

  6. Changes in pHin buffer The first task is to find the relative amounts of HisH+ and His

  7. Changes in pHin buffer For each mole of HisH+ there are 4 moles of His

  8. Changes in pHin buffer For each mole of HisH+ there are 4 moles of His The total number of moles of His + HisH+ = 100 mmoles meaning His = 80 mmoles HisH+ = 20 mmoles

  9. Changes in pHin buffer Now let’s add 60 mL of 1.0 M HCl The acid reacts with free base His Therefore, His and HisH+ concentrations are changed

  10. Changes in pHin buffer New concentrations: 20.0 mmol His is left behind 60.0 mmol HisH+ is generated 20.0 mmol of HisH+ was already present

  11. Changes in pHin buffer Thus total concentrations: His = 20.0 mmol HisH+ = 80.0 mmol

  12. Changes in pHin buffer

  13. Changes in pHin buffer pH = 5.4 Note that mmols are used instead of concn units since the volume is constant

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