What is the difference between k and pk

Sign in via your Institution. You could not be signed in, please check and try again. Sign in with your library card Please enter your library card number. Show Summary Details Overview pK value. All rights reserved. Sign in to annotate. Or, the larger the pKa value, the weaker the acid. Weak acids typically have pKa values between 2 and Kb is the base dissociation constant and pKb is the -log of this constant. The base dissociation constants are interpreted just like the acid dissociation constants.

A large Kb value means a base has largely dissociated and indicates a strong base. A small pKb value indicates a strong base, while a large pKb value indicates a weak base. The equilibrium constant for this reaction is the base ionization constant K b , also called the base dissociation constant:.

Once again, the concentration does not appear in the equilibrium constant expression.. Similarly, Equation The relative strengths of some common acids and their conjugate bases are shown graphically in Figure At the bottom left of Figure Have you ever performed a calculation using the equation below? You may recall that we define pH and pOH as follows:. It comes from the value for the equilibrium constant when water self-dissociates self-ionises or auto-dissociates :.

For which the expression for the equilibrium constant, K w , also known as the ion-product for water, is:. Remember the magic of using logarithms we discussed above? If you want to multiply two numbers you add their logarithms Similarly, if we know the solution's pH, we can calculate its hydrogen ion concentration in mol L -1 :.

We can write an expression for the equilibrium constant for this acid dissociation K a as given below:. We can therefore calculate the value of pK a for any weak acid if we know the value of its acid dissociation constant K a :.

And the strongest weak acid will have the largest K a but the smallest pK a. We can write an expression for the equilibrium constant for the dissociation of the base K b as shown below:. Therefore we can calculate the value of pK b for any weak base if we know the value of its base dissociation constant K b :.

If we are asked to compare two or more bases, the weakest base will have the smallest K b but the largest pK b. Take the test now! Each flask contains 0. The respective pK a values for the contents of each flask are as follows: 4.

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