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Define $\mathrm{p} K_{\mathrm{a}}$ for a weak acid. What is the relationship between the value of the $\mathrm{p} K_{\mathrm{a}}$ and the strength of the acid? Do the same for a weak base.

The lower the value of $p K_{a}$, the stronger is the acid.The lower the value of $p K_{b}$ the stronger is the base.

Chemistry 102

Chapter 16

Acid-Base Equilibria and Solubility Equilibria

Acid-Base Equilibria

Aqueous Equilibria

Carleton College

University of Central Florida

University of Kentucky

Lectures

00:41

In chemistry, an ion is an atom or molecule that has a non-zero net electric charge. The name was coined by John Dalton for ions in 1808, and later expanded to include molecules in 1834.

24:14

In chemistry, a buffer is a solution that resists changes in pH. Buffers are used to maintain a stable pH in a solution. Buffers are solutions of a weak acid and its conjugate base or a weak base and its conjugate acid, usually in the form of a salt of the conjugate base or acid. Buffers have the property that a small change in the amount of strong acid or strong base added to them results in a much larger change in pH. The resistance of a buffer solution to pH change is due to the fact that the process of adding acid or base to the solution is slow compared to the rate at which the pH changes. In addition to this buffering action, the inclusion of the conjugate base or acid also slows the process of pH change by the mechanism of the Henderson–Hasselbalch equation. Buffers are most commonly found in aqueous solutions.

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Define $\mathrm{p} K_{\mat…

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What is the relationship b…

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Which has the larger numer…

So for this question, we're gonna first look at the value of K A. Our key value is our ionization constant, where when a solution is that equilibrium okay is equal to essentially the ratio of the products over the reactive. And these are all concentrations. Now, this relationship can be rearrange to form the equation. Negative log of our concentration of hydrogen is equal to the negative log of K plus the log of the concentration are conjugated base over our initial acid. And this is for we're talking about in the context of week basis. You know that the relationship between the negative log of the concentration of protons is our pH. So similarly, the negative long of R K A. Is referred to as R p K value. And this gives us our Henderson Hasselbach route equation, which you'll be using to solve a lot more equilibrium problems later on. So now we can start looking at what is the relationship between our PK value and our strength of our acid? We know that the greater our K, the greater our product, and we know that's the strength of an acid is based on its ability to associate. The more dissociation that's occurring, the stronger the acid. And so the greater the K a, the stronger the acid. Whenever you take the negative log of something, however, this relationship gets flipped. So wherever you flip the relationship, you get that the greater the K value, the smaller the peat, a value and the greater the strength of an acid and then vice versa was smaller. The k a value, the greater the PK value and in the lower the strength of the acid. Now it's asking us for the relationship between PKK and a weak base. Now we know that the stronger an acid is the weaker of a base. It is the weaker the continent basis. So the greater the K value, the swollen PK value and then the smaller the strength of your base. Now you can take this entire relationship that we've built and flip it in terms of K B. So K B is your ionization constant for a weak base? Whenever you take it into perspective of a base, these relationships get flipped in the opposite direction. So really, keep in mind which values that you're using in whatever context that they're given

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