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10. Acids and Bases

Acid and Base Strength

10. Acids and Bases

Acid and Base Strength

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Strong Acids and Strong Bases are classified as Strong Electrolytes. While Weak Acids and Bases are Weak Electrolytes.

Understanding Acid and Base Strength

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Acid and Base Strength Concept 1

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now recall that strong acids and strong bases are classified as strong electrolytes, while weak acid and weak bases are weak electrolytes. Now, for a strong electrolyte, that means an acid that dissociates Orion eyes is completely in water and donates a proton. When we say proton, I mean H plus ion easily. We're gonna say a weak acid though only partially dissociates and donates a proton less readily and it favors reactivates. So if we take a look here at a strong acid versus a weak acid here we have hydrochloric acid, hydrochloric acid will will basically donate an H plus to water, thereby creating a three plus since HP Hcl is giving away an H plus what's left of it is C L minus. So basically think of this as a reaction. And what you have here on this side is your products, which is made up of H +30 plus ions and cl minus ions realize that this is a complete association of hcl so it'll be 0% left of this and you'll have 100% left of these products. It easily donates NH plus to the water. And it favors this product side because you're making 100% of it. On the other side we have HCM, which is hydro satanic acid, a weak acid. It will also donate an H. Plus to water. So you'll have the formation of some H +30 plus which will result in some CN minus being formed. But a vast majority of it will still be in the original form of H. C. N. So you're gonna stay here. We only associate partially. Only some of the H plus is donated over to the water and it's the reactant of H. C. N. That's greatly favored because even if we look here, you can see a vast majority of it is still in this shading, meaning a vast majority of it is still in the HCM form. So just keep this in mind when comparing my strong acid to a weak acid.

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Acid and Base Strength Concept 2

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we're gonna stay here that strong bases are basis that disassociate or ionized completely in water. And they have a high affinity for protons. That means they readily accept them. They want to accept H plus ions. Now, weak bases on the other hand, they only partially associate and they have a low affinity for protons and they favour reactors. So here we have examples of a strong base and a weak base. Here we have an hoh sodium hydroxide. It's a strong base. When it's placed into water, it completely ionized is into an A plus in O. H minus. You can see that there are no blue spheres left. All of them have been converted into these ions. So it dissociates completely. The presence of all of these O. H minus ions, opposites attract O. H minus is attracted to H plus And then we're making nothing. But these ions will make 100% of them. So products are highly favored, they need 0% left of this. On the other side we have an H3 Ammonia, which is a weak acid. I'm a weak base, sorry, weak base. So it can accept H plus and become NH four positive. It gets an H plus from water war donating NH plus two, it becomes a H minus. But you don't make many of these ions. In fact, if you look a vast majority of it is still in the bluish spears which represent ammonia. So we're not making very much of this. So we're making a very low percentage of these products. So the vast majority of it will stay in the NH 34 So it associates partially we have a low affinity for H plus since there is not O H minus being formed. And also because any street doesn't really accept an H plus And we we have a majority of its still in NH three forms. So reactions are highly favored now when it comes to strong acid and strong basis here are some basic ones that you should keep in mind when looking at strong acids and strong bases. So here we have a choice. I HPR HCR Yeah, your group seven a elements, iodine, bromine and chlorine. So if you look on the periodic table you put them next to an h baby coming acid. They represent strong acids. Here we have their oxygen forms. So we have Bureau four which is per bromate. Here, bromate, per chlorate and chlorate when they combined with H plus, they also make strong acids. Then we have sulfuric acid, nitric acid and then the hydro nia. My on rounding it out as our strong acids for strong basis. It's easy to see the pattern here. All of these are group one A metals connected to O H minus. So ally positive without H minus gives me a lie. Ohh okay, positive with O H minus gives me Kluh. So these are all your group won eight medals with an O. H. Here in group two way. It's a little bit trickier. It's not all the medals and group to a, it's just calcium strong team and very um when they combined with O H minus, they give us a strong base. So keep in mind this is a direct list of the strong acids and strong bases that you'll see when you're doing questions on acids and bases. So keep these in mind when looking at any questions dealing with acid or base strength.

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Acid and Base Strength Example 1

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here are going to say the following represent acquis acid solutions, identify the strong acid, weak acid and the weakest acid. Alright, so here we have a choice A which represents our weak acid and it's reacting with water here. The products that would form should be H 30 Plus and a minus. If you are a strong acid, you should make 100% of both of these products. You shouldn't have any H. Remaining. So if we look which one has no H. A. Remaining, remember H. A. Is this form here And we can see that's the Middle one. In the middle of all we have is a trio plus and a minus. So this is a strong acid. Then that would mean the next. The other two are either weak acid or weakest acid. Remember the weakest acid would form the least amount of these two ions. So if we look which one forms the least amount of those two ions, It looks like it is the last one. The last one forms the fewest amount of H30 plus that we can see right H30 plus is this and there's only one of it. And then here This one sphere by itself there goes right there. This one would be the weakest acid. This one he was weak. It only makes two of the hydro um the extra plus ions here and then has to a minus ions. All right, so remember a strong acid completely ionized it. So we make 100% of these two ions. So we should have none of this remaining. And then to compare the other to look at how much they make in terms of these products, the weakest one will make the fewest amount of these particular ions as products.

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Acid and Base Strength Concept 3

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we're gonna say there's an inverse relationship between strength of acids and bases and their congregants. A rule of thumb is a strong acid will have a relatively weak conjugate base. And in fact the stronger the acid, the weaker the conjugate base and that we conjugate base has a low affinity for proton. That means he doesn't want to accept an H. Plus. So here we have hcl reacting with water. Hcl is the acid, so it's gonna donate. NH plus to the water, Water becomes H 30. Plus. As a result, Hcl lost in H. Plus to what's left is C. L minus. It's conjugal base. For remember if you're strong acid, that means you're conjugate base will be weak. So here we're gonna have a week can't get base as a product.

Stronger the acid, weaker the conjugate base.

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Acid and Base Strength Concept 4

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All right. So remember, there's an inverse relationship. So that means a weak acid will have a relatively strong conjugate base. And in fact the weaker the acid, the stronger the conjugate base, a stronger conjugate base has a high affinity for protons. It has. It wants to more readily accept an H. Plus here we have HCM which is a weak acid, hydroxy tannic acid. It reacts with water, water except in H plus and becomes H +30 plus. As a result, eight cm gave away an H plus. Now at CN minus here, it's a weak acid. So that means it's going to be a stronger conjugate base. It's still weak but it's stronger because it came from someplace else that's weak. Now notice also that we have reversible arrows here. The arrow that points for the reactant is longer. That means reactors are more highly favored. This makes sense because remember, weak acids and weak bases don't completely ionized. We don't make 100% of these ions. A vast majority of it is still in the reacting form, which is why the arrow is pointing towards the reacted that side is more favored. There's more of it. So we're gonna stay here stronger the base, the weaker the conjugate acid, we conjugate acids less readily donate protons the week of the base than the stronger the conjugate acid, stronger acids more readily donate protons, or more easily donate protons. Just remember this inverse relationship. If you're strong in one particular way, you're weaker in the opposite way, a strong acid would equate to a weaker conjugate base.

Weaker the acid, stronger the conjugate base.

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Acid and Base Strength Example 2

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Which of the following assets will have relatively strong Kentucky basis. Remember a strong conjugate base comes from a weak acid. So basically we have to look and see which one here is a weak acid. So here we have panoramic acid, which is one of the strong strong acids. So this wouldn't work. Hydro sonic acid is a weak acid. So this would be an answer. Nitric acid is a strong asset. So that wouldn't work. And then we have per caloric acid, which is a strong asset, so that wouldn't work. Remember, a weak acid would equate to stronger or strong contract basis. So here, the only answer that works is option B.

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Problem

Problem

Which of the following is the strongest base?

A

NO₃^–

B

F^–

C

Cl^–

D

ClO₄^–

E

H₂O

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Problem

Problem

Which of the following bases will have the weakest conjugate acid?

A

CH₃COOH

B

KOCH₃

C

CH₃NH₂

D

NH₄OH

E

LiOH

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Problem

Problem

Which of the following aqueous species will contain mostly reactants?

A

CsOH

B

HNO₃

C

Sr(OH)₂

D

HClO₃

E

Mg(OH)₂

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Problem

Problem

Determine [OH^–] in each base solution. If the base is weak, indicate the value that [OH^–] is less than.

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Problem

Problem

Predict the direction of the following reaction:
HC₂H₃O₂ (aq) + H₂O (liq) ______________ H₃O⁺ (aq) + C₂H₃O₂^– (aq)

A

B

C

D

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PRACTICE PROBLEMS AND ACTIVITIES (6)