Table of Contents

## How do you find the Ka value?

As noted above, [H3O+] = 10-pH. Since x = [H3O+] and you know the pH of the solution, you can write x = 10-2.4. It is now possible to find a numerical value for Ka. Ka = (10-2.4)2 /(0.9 – 10-2.4) = 1.8 x 10-5.

**Is equivalence point equal to PKA?**

The equivalence point of an acid–base titration is the point at which exactly enough acid or base has been added to react completely with the other component. The pH at the midpoint, the point halfway on the titration curve to the equivalence point, is equal to the pKa of the weak acid or the pKb of the weak base.

**How do you find Ka given pH and molarity?**

1 Answer

- You start by using the pH of the solution to determine the concentration of the hydronium ions, H3O+ .
- By definition, the acid dissociation constant, Ka , will be equal to.
- Ka=[H3O+]⋅[A−][HA]

### How do you calculate Ka from pKa?

To create a more manageable number, chemists define the pKa value as the negative logarithm of the Ka value: pKa = -log Ka. If you already know the pKa value for an acid and you need the Ka value, you find it by taking the antilog. In practice, this means raising both sides of the equality to exponents of 10.

**What is KA equal to?**

The Ka expression is Ka = [H3O+][C2H3O2-] / [HC2H3O2]. The problem provided us with a few bits of information: that the acetic acid concentration is 0.9 M, and its hydronium ion concentration is 4 * 10^-3 M. Since the equation is in equilibrium, the H3O+ concentration is equal to the C2H3O2- concentration.

**How do you convert pKa to Ka?**

#### Why does pH equal pKa at equivalence point?

Because of the incomplete dissociation of the acid, the reaction is in equilibrium, with an acid dissociation constant, Ka, which is specific to that acid. point are the same. Therefore, at the half-equivalence point, the pH is equal to the pKa.

**Which is the correct formula for pH and Ka?**

1 Ka = [H+] [A-]/ [HA] 2 pKa = – log Ka 3 at half the equivalence point, pH = pKa = -log Ka

**What should the pH be at the equivalence point?**

2) The pH of the solution at equivalence point is dependent on the strength of the acid and strength of the base used in the titration. — For strong acid-strong base titration, pH = 7 at equivalence point. — For weak acid-strong base titration, pH > 7 at equivalence point.

## How to calculate the pKa of a compound?

To calculate the pKa values, one must find the volume at the half-equivalence point, that is where half the amount of titrant has been added to form the next compound (here, sodium hydrogen oxalate, then disodium oxalate). Halfway between each equivalence point, at 7.5 mL and 22.5 mL, the pH observed was about 1.5 and 4, giving the pKa values.

**How to find the Ka of monoprotic acid?**

Therefore, one can easily find the acid dissociation constant of the monoprotic acid by finding the pH of the point halfway between the beginning of the curve and the equivalence point, and solving the simplified equation. In the case of the sample curve, the Ka would be approximately 1.78×10-5 from visual inspection (the actual Ka2 is 1.7×10-5)