## How to compute pH of ((COOH)2) Oxalic acid?

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Dhamnekar Winod
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### How to compute pH of ((COOH)2) Oxalic acid?

pH of oxalic acid is given 5.4e-2 in table of equilibrium constants for acids and bases in aqueous solution. But, on other chemistry website , it is stated as
'' The constant acid dissociation of oxalic acid is 5.60 between 10⁻² and 5.42 between 10⁻⁵. As oxalic acid is a polyprotic acid, there are two values and it has a chemical formula HOOC-COOH."

What does this mean?

HO2CCO2H⇌H⁺ + HOOCCOO⁻ 📖 Assuming 1.0 M of ((COOH)2) aqueous solution, Ka=54e-2= x²/(1-x)→ x=0.207

So,pH= -log(0.207) =0684

But in table, pH=1.27 How is that?
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
ChenBeier
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### Re: How to compute pH of ((COOH)2) Oxalic acid?

pH 1.27 is for 0.1 mol/l not for 1 mol/ l
Dhamnekar Winod
Sr. Staff Member
Posts: 149
Joined: Sat Nov 21, 2020 10:14 am
Location: Mumbai[Bombay],Maharashtra State,India

### Re: How to compute pH of ((COOH)2) Oxalic acid?

What is the value of second equilibrium constant for HOOC-COOH? Is it 5.42e-5?
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
ChenBeier
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Posts: 742
Joined: Wed Sep 27, 2017 7:25 am
Location: Berlin, Germany