Dissociation Constant of Weak Acids

AI Thread Summary
To calculate the pH and dissociation constant (Ka) of an unknown weak acid at a concentration of 0.20 mol/L, one must first measure the pH of the acid or know its Ka. The initial assumption that Ka equals (0.20)^2/0.20 is incorrect without pH data. A pH titration can provide necessary data to create a titration curve, which can be used to determine Ka. Resources such as Borek's online guidance and studies on neutralization titrations for weak acids may assist in understanding the process. Accurate calculations depend on proper measurement and analysis of the acid's behavior in solution.
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Homework Statement


In my lab, it says that i have to calculate the pH and the Ka of an unknown acid of known concentration (0.20 mol/L)..however, the part that is confusing me is that we first had to obtain 40 mL of that particular unknown acid...

Homework Equations





The Attempt at a Solution


I know that [HA]--> <--- [H]+ +[A]- ..i initially thought that it's Ka is simply (0.20)^2/0.20 but i think it's wrong...
 
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You either MEASURE the pH of the unknown acid, or you KNOW THE Ka or identity of the acid. Other than that, you perform a pH titration and make a TITRATION CURVE. Your Ka expression can be coordinated to certain data from your pH titration data (or the curve). Borek has some online guidance that may help with this theory. Another choice is to study the theory of neutralization titrations, especially for weak acids and bases.
 
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