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pH calculation check

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  • Tony & Elle Ackland
    Could some keen chemist please check my calculations .... using ... Citric acid : C6O7H8 Mw=192, Ka=7.4x10-4 Tartaric acid : C4O6H6 Mw=150, Ka=1x10-3 Citric
    Message 1 of 1 , Feb 9, 2001
      Could some keen chemist please check my calculations ....

      using ...
      Citric acid : C6O7H8 Mw=192, Ka=7.4x10-4
      Tartaric acid : C4O6H6 Mw=150, Ka=1x10-3

      Citric acid:

      1g in 1L of water gives 0.005521 mol/L which results in a pH of 2.7 ?
      or to get a pH of 4 .... need only 0.022 g/L (eg 0.44g in 20L)

      Tartaric acid:

      1g in 1L of water gives 0.00667 mol/L which results in pH of 1.45 ?
      or to get a pH of 4 .... need only 0.016 g/L (eg 0.33g in 20L)

      or to put it into more conventional terms, the 3/4 teaspoon of supermarket
      grade citric acid I've added to 20L wash has probably acidified it WAY past
      a "yeast happy" pH of 4 and it probably needs a decent dose of bicarbonate
      of soda to neutralise it ?

      ...which...at a Mw of 84 g/mol for bicarb, means I should add about 0.44 g
      of bicarb for each 1g of citric acid ?

      I knew that high-school chemistry would finally come in usefull (just a
      week too late)

      Tony
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