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Topic: pH for binary acid soultion  (Read 5370 times)

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hjjou

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pH for binary acid soultion
« on: July 08, 2004, 01:41:36 PM »
Hi,
I would like to know what euation I should use when I am try to calculating the pH of a binary acid soultion (e.g. a mixture solution with acetic and lactic).  For a simple acid solution, I can use the equation pH=pKa+log[A-]/[HA], what I don't quite clear is how can I calculate the pH or concentration of a more complicated solution like binary acids system with known pkas for the acids.  Thanks for any input.

Offline Donaldson Tan

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Re:pH for binary acid soultion
« Reply #1 on: July 08, 2004, 01:51:28 PM »
Simultaneous Equations.
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

hjjou

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Re:pH for binary acid soultion
« Reply #2 on: July 08, 2004, 01:57:42 PM »
To Geodome:

Thanks for replying.  What are Simultaneous Equations?  I am not a Chemistry student, this is work related.  Can you explain a little more or refer me to any literature?  Thanks.

Offline AWK

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Re:pH for binary acid soultion
« Reply #3 on: July 09, 2004, 04:38:32 AM »
For weak acid solution
pH= -log(SQRT(Ka x c))
For mixture of a few weak acids
pH=-log(SQRT(K1 x c1 + K2 x c2 + ...))

Your equation is used for buffer solutions.
« Last Edit: July 09, 2004, 05:09:18 AM by AWK »
AWK

hjjou

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Re:pH for binary acid soultion
« Reply #4 on: July 09, 2004, 09:17:22 AM »
To AWK:

Thanks so much.

So I used the wrong equation?

Is there a textbook or literature I can read?

Offline AWK

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Re:pH for binary acid soultion
« Reply #5 on: July 12, 2004, 04:11:11 AM »
Your eqaution is true but useless for pH calculation of weak acid because it contains two unknown variables.

read on weak acids in university textbooks on general or physical chemistry
AWK

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