How do you find KA and KB values?

Asked By: Rainer Rauprich | Last Updated: 13th May, 2020
Category: science chemistry
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General base dissociation in water is represented by the equation B + H2O --> BH+ + OH-. Ka and Kb values measure how well an acid or base dissociates. Higher values of Ka or Kb mean higher strength. General Ka expressions take the form Ka = [H3O+][A-] / [HA].

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Furthermore, how do you find KB from Ka?

Solve the equation for Kb by dividing the Kw by the Ka. You then obtain the equation Kb = Kw / Ka. Put the values from the problem into the equation. For example, for the chloride ion, Kb = 1.0 x 10^-14 / 1.0 x 10^6.

Also Know, what is the kb value? Kb value refers to a standardized ASTM test that measures the relative strength of a non-aqueous cleaning fluid. Mild solvents with lower Kb values will may not be strong enough to dissolve ionics and fluxes.

Simply so, how do you find the Ka value?

Note that x is Related to pH and Calculate Ka 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.

What is the difference between KB and Ka?

Ka is the "acid dissociation constant." It deals with the concentration of H + ions. Kb is the "base dissociation constant." It deals with the concentration of OH - ions.

32 Related Question Answers Found

What does pKa mean?

Key Takeaways: pKa Definition
The pKa value is one method used to indicate the strength of an acid. pKa is the negative log of the acid dissociation constant or Ka value. A lower pKa value indicates a stronger acid. That is, the lower value indicates the acid more fully dissociates in water.

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.

What is the relationship between KA and KB?

To summarize: Ka * Kb is equivalent to adding the acid and base reactions together, which results in a net equation of the autoionization of water. It's not a neutralization/acid-base reaction, but I think the Kw = Ka * Kb is a mathematical relation made to expedite calculations.

What is the Ka of HCl?

Ka Acid
1.0 * 109 Hydrobromic acid HBr
1.3 * 106 Hydrochloric acid HCl
1.0 * 103 Sulfuric acid H2SO4
2.4 * 101 Nitric acid HNO3

What is Ka KB and KW?


pKa and pKb are the -logs of Ka and Kb; Ka and Kb, when multiplied, are equal to Kw (1.0x10^-14). Kw is also equal to the hydronium and hydroxide concentrations when multiplied.

How do you convert pKa to Ka?

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.

Can pH be negative?

It's definitely possible to calculate a negative pH value. In practice, any acid that yields a concentration of hydrogen ions with a molarity greater than 1 will be calculated to have a negative pH. For example, the pH of 12M HCl (hydrochloric acid) is calculated to be -log(12) = -1.08.

What is KW pH?

Before discussing pH we must understand the equilibrium behavior of water. The equilibrium constant, Kw, is called the dissociation constant or ionization constant of water. In pure water [H+] = [OH-] = 1.00x10-7 M. pH and pOH. Working with numbers like 1.00x10-7 M to describe a neutral solution is a rather inconvient.

Is pKa the same as pH?

The pH is a measure of the concentration of hydrogen ions in an aqueous solution. pKa (acid dissociation constant) and pH are related, but pKa is more specific in that it helps you predict what a molecule will do at a specific pH.

What are the units of Ka?


An acid dissociation constant (Ka) is a quantitative measure of the strength of an acid in solution. The dissociation constant is usually written as a quotient of the equilibrium concentrations (in mol/L): [latex]K_a = frac{[A-][H+]}{[HA]}[/latex] .

What is the kb value of NaOH?

What Is the Kb of NaOH? The base dissociation constant, or Kb, of sodium hydroxide, or NaOH, is approximately 1020.

Can pKa be negative?

A pKa may be a small, negative number, such as -3 or -5. It may be a larger, positive number, such as 30 or 50. The lower the pKa of a Bronsted acid, the more easily it gives up its proton. The higher the pKa of a Bronsted acid, the more tightly the proton is held, and the less easily the proton is given up.

What is the difference between pKa and Ka?

Ka is acid dissociation constant and represents the strength of the acid. pKa is the -log of Ka, having a smaller comparable values for analysis. They have an inverse relationship. Larger the Ka, smaller the pKa and stronger the acid.

What does a high pKa mean?

A lower pKa means the Ka value is higher and a higher Ka value means the acid dissociates more readily because it has a larger concentration of Hydronium ions (H3O+).

What do pKa values tell you?


pKa is a property of a compound that tells us how acidic it is. The lower the pKa, the stronger the acid. pH is a property of a particular solution that depends on the concentrations and identities of the components. If the pH is lower than the pKa, then the compound will be protonated.

What is the kb of water?

List of boiling and freezing information of solvents
Solvent Boiling point (°C) Kb (°C/mol/kg)
Naphthalene 217.9
Nitrobenzene 210.8 5.24
Phenol 181.75 3.60
Water 100.00 0.512

Does higher KB mean stronger base?

A large Kb value indicates the high level of dissociation of a strong base. A lower pKb value indicates a stronger base.