Bases Introduction - Video Tutorials & Practice Problems
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concept
Intro to Bases
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Now, a base is any substance that can neutralize an acid within a chemical reaction. Now, here we're gonna break down bases into either being ionic bases or covalent bases for ionic bases. We're going to say these are ionic compounds containing a metal CT ion. So a positive metal connected to a basic anion. Now, the basic anions are hydroxide ions, hydride ions amide ions and oxide ions. So what do they look like? Well, hydroxide is oh minus hydride is H minus an amide is NH two minus. Now pay close attention amide is made up of nitrogen and hydrogen. So it's, it's an amine and it's negatively charged and then oxide is 02 minus. We said that ionic um ionic bases basically have these basic ions and ions connected to a metal cat ion. So let's put here lithium ion. Uh let's put here calcium ion here. Let's do sodium ion and let's do Barry I on here. So here, remember when the numbers and the charges are the same, they just simply cancel out and then we just have lioh. So this is lithium hydroxide. In this one, the numbers are different within the charges So they crisscross, remember you only crisscross the numbers don't worry about the charges. So this would be calcium hydride. Here, the numbers are the same, they cancel out. So this would be sodium amide and then both the numbers are the same, they cancel out. So this would be barium oxide, some examples of typical ionic bases. Now here covalent bases, we're gonna say this is restricted to our neutral amines. Remember what is an amine? These are compounds composed of just nitrogen and hydrogen or carbon, nitrogen and hydrogen. So just remember when we look at a base, we can either look at at it as an ionic base or a covalent base.
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example
Bases Introduction Example
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Which of the following represents the possible structure of a base. So remember, bases can either be ionic bases or they could be covalent bases for the first one. We have Coh four. All right. So if we take a look at this, this would not be an ionic base since it doesn't have a metal cion involved, it's only nonmetals there and it wouldn't be a neutral base either because it's not an amen. So this would not be an answer for BB isn't a mean because it's composed of nitrogen and hydrogen. But remember typically, we're gonna say the neutral means are what's gonna be classified as a base. Positive means we've talked about before in earlier videos positive a means are typically acidic. So this would not work. C is an answer because in C we have potassium which is a metal connected to hydroxide ion. See it was K positive Noh minus that combined to give us potassium hydroxide. Then finally, D doesn't work because D is a covalent compound that begins with the hydrogen, which is a simple way of looking at this being an acid. So out of all the choices only option, C represents a typical base.
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concept
Characteristics of Bases
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Now like acids, bases share certain similar characteristics when placed in aqueous solutions. Here, we're gonna look at the dissolution of bases. We're gonna look at paste and field and then we're gonna look at litmus paper. So bases just like acids will ionize when placed in water. So here we have an example of sodium hydride. Sodium breaks up into N A plus one aqueous. And then we have the hydride ion. Remember the hydride ion represents a basic anion. And then here we have strontium hydroxide. Strontium is a group two way. So it's sr two plus aqueous. And then we have two hydroxide ions, aqueous taste and feel we're gonna say here that bases have a bitter taste. So a good way to remember is bases with b bitter with B and we're gonna say they are slippery to the touch, believe it or not. When we look at soap, soap represents a base. So just remember the way they taste, they are bitter and they are slippery to the touch. Think of soap as a way of of remembering how bases can be used in everyday use. Now, litmus paper remember litmus paper reacts uh just in the same way as acids and can, we can use litmus paper on acids, we can use litmus paper on base. Now, here, though, the litmus paper reacts to the presence of the basic anion here, a base, we're gonna say it changes a red litmus paper into blue. So you take your red litmus paper, you dip it into the basic solution and when you pull it out, the red litmus paper has, can transition to a bluish color. So keep these in mind when we're talking about the basic characteristics of a base.
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example
Bases Introduction Example
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Which of the following is a characteristic of a strong base. So here, when we look at these options, it doesn't matter if it's a strong base or a weak base. These are characteristics that are addictive of all bases. All right. So here it turns blue, litmus paper red. Well, remember that happens not with bases, but with acids, it releases H plus ions in a solution. No, when we talk about a base, it ionizes into a basic anion which H plus is not, it removes oh minus ions in a solution. So here, if we had, for example, lithium hydroxide that would produce oh minus, it wouldn't remove oh minus. So this can't be true. It can be used in production of cleaning supplies. Remember taste and feel we said that bases taste bitter, but more importantly, they feel slippery. And we use an example of a bar of soap that's because bases can be used within cleaning supplies. So here option D is a correct answer.
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Problem
Problem
Which of the following compounds will turn a piece of red litmus paper to a bluish color?
a) HI b) C6H5NH2 c) CH3COOH d) HOCN
A
HI
B
C6H5NH2
C
CH3COOH
D
HOCN
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