Bronsted-Lowry Acids and Bases - Video Tutorials & Practice Problems
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concept
Bronsted-Lowry Acids vs Bases
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Here, we're going to say that in 1923 Johannes Bronte and Thomas Laurie develop a new definition for acids and bases. Here, we're going to say that the Bronson Lore a definition is that it is a proton donor. So, acids donate H plus to water producing H +30 plus ion which is coined the hydro ion. Here we take a look, we have hydroponic acid reacting with water. Here, hydroponic acid is serving as our Bronson acid. So it's going to donate H plus visually. If you wanna think about it, you can think of it like this like it's giving away its H plus. And in doing that H2O accepts it. So H2O is acting as our base. What's the result of these actions? Well, we're going to say here that H pr gave away an H plus. So all that's left of it is BR minus H2O accepted in H plus. And as a result, it creates H +30 plus. Now brau Lari base is a proton acceptor. If we take a look here, we have ammonia reacting with water. In this case, ammonia acts as the base. So it's going to accept H plus and it is water that will be donating the H plus. So visually think of it H plus is gonna go here. What's gonna happen as a result? Well, NH three picks up an H plus and becomes NH four positive as a product. So here water is acting as the acid and then water gateway in H plus. So what's left of it? Well, what's left is oh minus. So that's what we have left of our water molecule. So just remember, this goes a little bit further into our understanding of what constitutes an acid will, constitutes a base, an acid will donate H plus and a base will accept H plus.
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example
Bronsted-Lowry Acids and Bases Example
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Identify each compound as either Bronin acid or base. So for the first one, we have ammonium ion, this represents a positively charged amine, remember positively charged amines are weak acids. So here this would be a Bronin acid. For B we have lithium hydride, we have a group one, a metal connected to the hydride ion. This represents an ionic base in it. It's the hydride ion which is negatively charged that would accept an H plus. So this would be a base. Next, we have ach three NH two. This is methyl amine, it's a neutral amine, neutral amines are weak bases. So this is a brony base. It could accept NH plus and if it did, it would create CH three NH three plus one. And then finally, here we have H two te, this represents a binary acid. So it could donate one of its H pluses. If it did that, it would become HTE minus. So this is how we classify each of the compounds given to us within this example question.
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concept
Comparing Bronsted-Lowry and Arrhenius
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Now let's take a look at some questions that try to relate Aous acids and bases to Bronston Laurie acids and bases. The first question says, are all aous acids and bases considered Bronston Lori acids and bases. The answer to this question would be a yes. So for example, we have hydro Bromma acid under the arenas definition, it would be an acid since it produces H plus ion. But it would also be a Brosel Loic acid because it is donating an H plus ion. So under that definition, it would be both an aous acid and a prosy loic acid. Now, sodium hydroxide here, sodium hydroxide under the aous acid and base definition is a base because it produces oh minus. Now this oh minus could accept an H plus from the water molecule surrounding it. So it would also be a Bronston lorry base. Now are all Bronston Laurie bases considered Arne spaces. The answer here would be a no. We're gonna say bases that do not contain oh minus hydroxide ion are not orus bases. Here we have ammonia ion. When you put it into water, it doesn't immediately produce oh minus in the way that we are accustomed to seeing under the uranus definition. Yes, it could accept an H plus ion from water to create oh minus, but it itself is not releasing oh minus into the solution. Now finally, are all Brony Loic acids considered aous acid. This would be a yes, because what is a Brony acid? It is an H plus donor. So it has H plus present meaning that if I put it within an aqueous solution, it will release H plus ions. So it would be an aous acid too. From this information, we can see that bronze and Lori takes a much more broader view of acids and bases than IUS does. Orus is much more limited in its scope. Bron and Lori is much more broad. So we can fit even more compounds under the definition of either an acid or a base.
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example
Bronsted-Lowry Acids and Bases Example
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Identify each compound as either a Bronston Laurie acid or base or Rous acid or base or both. So, here in the first one, we have carbonic acid, carbonic acid can dissociate into H plus ions. When we place it within an aqueous solution, this would make it an IOUs acid at the same time, since it can dissolve into H plus ions. When placed into an aqueous solution, it could technically donate, donate that H plus as well. So it also represent a Bronster Loic acid. So here we're gonna say it's both an aous acid and a Bronston Lori acid. So we'll say it's both. Next, we have methylamine. This is a neutral amine. Remember, neutral amines represent weak bases because it is a neutral amine. It could accept an H plus and therefore represents a Bronson Laurie base. However, it is not a metal hydroxide dissolving it in an aqueous solution does not allow it to release Noh minus from itself. So it would not be an IOUs base. So here it is only a Bronson Lori base which we're gonna abbreviate as BLB. Next, we have potassium amide. This represents a strong base because it is a base, it could accept NH plus ion from the water molecules around it. Once you place it within an aqueous solution, so it can serve as a brony base. Again, it is not composed of a metal hydroxide. Therefore, it doesn't release oh minus from its um dissolution. So we couldn't say that it is a uh a Rous base. So this is just gonna be a Boston Laurie base. Next, we have strontium hydroxide. It is the metal hydroxide. So it is in a space. It also has a presence of oh minus which could accept an H plus. And therefore, it represents a Bronston Lorie base. So we're gonna say here this is in areus base plus a B la base. So we say it is both. Next, we have Hydrofluoric acid. HF it could release H plus when dissolved in a solution. So it represents an aous acid and because it can release an H plus ion, it could donate that H plus ion. So it is also a Brost Loic acid. So we're gonna say it's an reus acid plus a Brost Loic acid. So it's both. And then finally, we have calcium hydride. Calcium hydride is a strong base here. The presence of the hydride ion H minus, it could accept an H plus ion. So it is a Bronte Lori base, but it is not a metal hydroxide. So we won't say that it represents an IOUs space. So here we're just gonna say it's a Bronston Lori base and that's how we classify each one of these compounds.
5
concept
Conjugate Acid-Base Pairs
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Now, Bronston, Lori acids and bases occur in what we call conjugate pairs. We're going to say when a base accepts a proton, remember, proton is H plus, it transforms into a conjugate acid. So basically, to create a conjugate acid, we have to add an H plus to a base. Here, we have methyl amine. Here, I've drawn lone pairs on the nitrogen. Um It possesses those lone pairs because when methylamine gains an H plus, it goes to the nitrogen carbon is already making all the bonds it can make. So by accepting this H plus, we get now ch three NH three positive, this is methyl ammonium ion. This represents the conjugate acid. Now, when an acid donates a proton, it transforms into a conjugate base. So basically, when you remove an H plus from an acid, you create a conjugate base. Here, we have nitric acid, we're gonna remove an H plus from it. When we do that, we're gonna create the nitrate ion. The nitrate ion is the conjugate base of my nitric acid, right? So just keep this in mind when we're talking about bro and Lori acid definitions of acids and bases, we're going to say here, if you are adding an H plus to a base, you create a conjugate acid. If you're removing an H plus from an acid, you're creating a conjugate base.
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example
Bronsted-Lowry Acids and Bases Example
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Here, it says to provide the formulas of the conjugates for each of the following compounds. So remember if we're given an acid, that means we have to show the conjugate base. If we're given a base, then we have to show the conjugate acid. If we take a look here at the first one, NH two and H two, that is a neutral amine, its name is hydrazine, but you don't need to know that it's a neutral amine. Therefore, it is a weak base. Since it is a base, we have to show the conjugate acid. Remember to give the conjugate acid, you add an H plus to it. So here we would get NH two NH three positive or you could just put the H plus on the first nitrogen. Either one would be correct. Next, we have, looks like an oxy acid. So this is formic acid, since it's an acid, we have to show the conjugate base. So we have to remove an H plus. So when we do that, we're going to get cho two minus. Next, we have hydrogen sulfate. This compound is amphoteric or hy protic. It has the presence of a hydrogen in the front and a negative charge. Remember, amp protic or amphoteric species can act as an acid or base depending on what they're reacting with. And because of this, I have to specify, does this amphoteric specie represent a base or an acid? Here, I'm saying it represents a base which means you need to show the conjugate acid to show the conjugate acid, you add an H plus to it. So here the conjugate acid would be H two. So four sulfuric acid and then finally, we have here um chorus acid, it is an acid. So I need to show the conjugate base. So we remove H plus when I do that, I get clo two minus I get the chloride ion, right? So these will represent each of the conjugates for the following compounds.
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Problem
Problem
Identify conjugate acid and conjugate base in the following reaction.
H2PO4− (aq) + H2O (l) ⇌ HPO42− (aq) + H3O+ (aq)
a) HPO42− (conjugate acid), H3O+ (conjugate base)
b) HPO42− (conjugate base), H3O+ (conjugate acid)
c) H2PO4− (conjugate acid), H2O (conjugate base)
d) H2PO4− (conjugate base), H2O (conjugate acid)
A
HPO42− (conjugate acid), H3O+ (conjugate base)
B
HPO42− (conjugate base), H3O+ (conjugate acid)
C
H2PO4− (conjugate acid), H2O (conjugate base)
D
H2PO4− (conjugate base), H2O (conjugate acid)
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Problem
Problem
In the following reaction, label Bronsted-Lowry acid and base, along with conjugate acid and base.
H2C6H6O6 conjugate acid H2O conjugate base HC6H6O6− base H3O+ acid
B
H2C6H6O6 acid H2O base HC6H6O6− conjugate base H3O+ conjugate acid
C
H2C6H6O6 conjugate base H2O conjugate acid HC6H6O6− acid H3O+ base
D
H2C6H6O6 base H2O acid HC6H6O6− conjugate acid H3O+ conjugate base
9
concept
Strength of Conjugate Acids and Bases
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50s
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We're gonna say there's an inverse relationship between strengths of acids and bases and their conjugates. 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 the weak conjugate bates 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 an H plus to the water. Water becomes H +30 plus as a result, HCL lost in H plus. So what's left is CL minus? It's conjugate base four. Remember if you're a strong acid, that means your conjugate base will be weak. So here we're gonna have a weak conjugate base as a product.
10
concept
Conjugate Acid-Base Relationships
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1m
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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 proton. So it has, it wants to more readily accept in H plus. Here we have HCM which is a weak acid. Hydro cyanic acid. It reacts with water, water accepts in H plus and becomes H +30 plus as a result, HCM gave away in H plus. Now it's C and minus here, it's a weak acid. So that means it's gonna 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 to the reactant is longer. That means reactants are more highly favored. This makes sense because remember, weak acids and weak bases don't completely ionize. We don't make 100% of these ions. A vast majority of it is still in the reactant form, which is why the arrows pointing towards the reacted that side is more favored. There's more of it. So we're gonna say here stronger the base, the weaker the conjugate acid, weak conjugate acids less readily donate protons, the weaker the base, then the stronger the conjugate acid, stronger acids more readily donate protons or more easily donate protons. So 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.
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example
Acid and Base Strength Example
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Which of the following acids will have relatively strong conjugate bases. So 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 per Bromma acid, which is one of the strong be strong acids. So this wouldn't work. Hydroxy acid is a weak acid. So this would be an answer. Nitric acid is a strong acid. So that wouldn't work. And then we have perchloric acid, which is a strong acid. So that wouldn't work. Remember a weak acid would equate to stronger or strong conjugate bases. 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
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
A
CH3COOH
B
KOCH3
C
CH3NH2
D
NH4OH
E
LiOH
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