When certain group one A and two way metals combined with any of the following anions, they form strong bases. These anions are our basic anions. They include hydroxide ion which is oh minus hydride ion which is H minus Gide ion which is NH two minus. And then finally, your oxide ion which is 02 minus. Remember when it comes to group one A and two A group one, a metals have a charge of plus one and group two A medals have a charge of plus two. In group one A we shade out the hydrogen. It's not a metal and the group one, a metals that we're talking about are lithium, sodium, potassium rubidium and cesium. Realize here that francium which is below cesium is not present because it's radioactive. It's kind of unpredictable in which it behaves. So we don't include it as one of the group one A metals in group two A, we gray out beryllium and magnesium. They're not included as these certain types of group two A metals. The certain types of group two A metals include calcium strontium and barium. Realize just like francium, we have radium which is below barium, it's not included because again, it's so large, it's a little bit unpredictable. So we don't include it in our definition of basis. Now, here we could choose any of these group, one A and two A medals that I've written and combine them with one of these four basic anions to create a strong base. So let's say I, I chose lithium here. This is plus one. This is minus one when the numbers and the charges are the same, they just cancel out. So this is just lithium hydroxide. Then let's say I chose strontium here. The numbers in the charters are different when they're different. They crisscross just worry about the numbers. Don't worry about the charge. So this would be strontium hydride here if we use N A plus one with the amide ion do so give us sodium amide. And then finally here I could use calcium with the oxide. The numbers are the same. So they cancel out. So this just becomes calcium oxide. So just remember these are the certain types of group one, a metals and group two a metals that can combine with our four basic anions to create a strong base.
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example
Bases Example
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Which of the following represents a strong base. Now, remember certain group one A and two A metals need to be combined with a basic an I, we take a look at the options. Beryllium and magnesium aren't part of the certain types of group one A or two A metals. So A wouldn't be an answer. D wouldn't be an answer. If we look at our remaining options, we have sodium lithium and potassium. Yes. Those are these certain types of group one a metals that could potentially create a strong base if they combine with the right basic anion here, sodium, if it combined with the oxide ion could make a strong base, but we have a problem. Remember the numbers are different. So they crisscross two comes here. One comes here. Sodium oxide would actually be N A 20. This is not sodium oxide. This is actually sodium super oxide. It's not a strong base for the next one. We have lithium ion and it's combining with the amide ion to give us lithium amide. So this is a strong base. It's the right group one, a metal with one of the basic anions in the form of the amide ion. And then finally, e we have potassium, which is good, but it's connected to Hypo acid. Hypo acid does not represent one of our four basic anions. So this will not make a strong base. So here, the only answer that gives a strong base is option c in the form of lithium amide.
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concept
Strong Base vs Weak Base
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Now, following acids, we're going to say that strong bases are strong electrolytes and weak bases are weak electrolytes. Now with strong bases, we're gonna say because they're strong electrolytes, they associate or ionized completely in water and are strong proton acceptors. Remember when we say the term proton, we just mean H plus. So they readily accept an H plus I now weak bases. On the other hand, because they're weak, they only partially dissociate. They don't completely ionize into ions and they are weak proton acceptors and they favor reactants. If we take a look here, we have sodium hydroxide, which is a good example of a strong base. And then as a weak base, we have ammonia here, sodium hydroxide completely ionizes when we throw it into water. So it breaks up to form 100% of sodium ion and hydroxide ion dissociates completely. We're going to say here that it is a strong proton acceptor. This oh minus that's created could gain an H plus from the water surrounding surrounding it. We'll talk about that in greater detail later on. And then here, since we make 100% of our products, that means we'll have no reactants left. So this reaction heavily favors the formation of products. Now, for weak basis, ammonia is a weak base. It's a positive amine here because it's a weak base. Very little of these ions are formed. So we're gonna have a small arrow pointing towards the product side. A vast majority of it will exist in its molecular form in NH three. So we show a larger arrow pointing in the opposite direction. So here it only partially associates. So we make way less than 100% of these ions. It is a weak proton acceptor and we're heading towards the reactant side. So the reactants are more favored than the products. So keep this in mind when we're looking at the differences, at least in terms of dissociation of strong bases versus weak base.
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example
Bases Example
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Which of the following bases will partially dissolve when placed in water. So partially dissolves means it partially dissociates or ionizes. So we're looking for the weak base out of all the options. If we were to take a look, remember, strong bases are formed when certain group one A and two A metals combine with the basic anion. If we take a look at the options. Lithium sodium susi and potassium are those certain types of group one a metals. So they could potentially make strong bases if they combine with the right basic anion, aluminum aluminum. On the other hand, is not one of those certain types of group one A and two A medals. In fact, it's not even found in group one A or two A, it's a group three a medal. And because of that, it's not going to constitute a strong base. It's going to be a weak base. It's still a base. Since it's aluminum, a metal cion connected to hydroxide ion, a basic ion. OK. Since it's weak, it only partially dissolve. If we take a look at the other options, if we look, we have lithium here connected to hydroxide ion this combination can make a strong base. Here, we have sodium ion connected to the amide ion. This also can make a strong base. Here, we have cesium oxide. So cesium here which is plus one is connected to the oxide ion +02 minus. This combination can make a strong base. And then finally, we have potassium hydroxide. So potassium is K plus one hydroxide is oh minus one. So here this combination can make a strong base. So out of all the options, only option c makes a weak base which only partially dissolve when placed in water.
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concept
Amines
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Now we call that an amine is a covalent compound containing nitrogen and hydrogen or carbon nitrogen and hydrogen, it doesn't have to be in that order as long as it contains carbon nitrogen and hydrogen in some way. Now, we're going to say that a means up to this point, we're going to take a look at neutral means and positively charged a means here, we're going to say that neutral means represent weak bases. So here we have three types of a means within the structure. And if we look at positive A means those with positive charges, they represent weak acids. And here we have the positive charge associated with each of these amines. So, amines are pretty unique because they can exist as either acids or bases. So it's always important to take a look. Does your amine have a charge of positive? If it does, it's going to be a weak acid. Is it neutral? It'll be a weak base. Now, we've also talked about another type of amine amide ion, which was represents one of the four strong basic anions. That's something else en entirely but realize here that yes, technically a means can have all three types of situations where they're positive, neutral and negative. But for right now, just remember the neutral ones are weak bases, the positively charged ones are weak acids.
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Bases Example
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Here, it says to identify the amine that will likely accept a proton. Remember, a proton is H plus when in the presence of an acid. All right. So first of all, it says an amine. Let's see which ones don't represent a means a means themselves possess nitrogen and hydrogen or carbon nitrogen and hydrogen. In some way, if we take a look, C is not an amine because of the presence of sulfur and it doesn't even have nitrogen. He is also not in a mean because here there's no nitrogen present, there's carbon and hydrogen, but where's the nitrogen? Next? It says we weakly accept a proton when in the presence of an acid, weakly accept a proton. Remember that's the definition of a weak base. Here. A B and D are all means. But remember, it's the neutral means that represent weak bases, positively charged do means represent weak acids. So here this is a weak acid since it's positively charged, this is a weak acid, since it's possibly charged the answer here would be option B that represents a neutral amine. Therefore, it's a weak base and it'll weakly accept a proton from an acid.
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Problem
Problem
Which of the following bases would more greatly favor the product side of a chemical reaction?
a) BeH2 b) H2Se c) SrH2 d) Pb(OH)4 e) HF
A
BeH2
B
H2Se
C
SrH2
D
Pb(OH)4
E
HF
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Problem
Problem
Which of the following compounds would be found as mostly molecules when placed into water?
I. Be(OH)2 II. HNO3 III. LiOH IV. (CH3)2NH V. CaO