Acids Introduction - Video Tutorials & Practice Problems
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concept
Common Acids
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Hey, everyone. So in our discussion of acids, recall, acid themselves are covalent compounds that have a hydrogen ion connected to a nonmetal anion or a poly atomic ion. Remember an ion is just a negatively charged ion. We're gonna say generally the hydrogen ion is at the beginning of the compound except for cases such as acetic acid and uh positive amines. And when we say amines, remember, amines themselves are covalent compounds that are containing nitrogen and hydrogen or carbon nitrogen and hydrogen. If we take a look here at some common types of acids, we have HCL which is hydrochloric acid. H two S which is hydro sulphuric acid, HCN which is hydro cyanic acid, we have phosphoric acid. And then if we look at the last three, we can see in the first four, they're covalent compounds made up of only nonmetals and they have hydrogen in the beginning. So that's a dead giveaway that we have an acid. But in the final three, we have acetic acid here. So remember acetic acid, common way of writing it is ch three coo H here, the hydrogen is at the end if it's written in this form we could also have it written in another form which you might see in that form. It follows the common setup of an acid where hydrogen is in the beginning, followed by C two H 302. So both of these ways are showing acetic acid. And then in the last two, we have positive amines. This one here is the ammonium ion. It is an amine because it is composed of nitrogen and hydrogen. It's an acid because it's a positively charged amine. And then over here we have methyl ammonium ion. It is also in a mean because it's composed of carbon nitrogen and hydrogen, it is also acidic because it is positively charged. Later on, we'll talk about negatively charged and um not charged amines. Just for now, remember that acids, we, if we have a positively charged amine, it constitutes an acid. All right. So just keep this in mind as general ideas when it comes to uh most types of acids that you'll see.
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example
Acids Introduction Example
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Which of the following does not represent the possible structure of an acid. So if we take a look at the first one, we have H pr this is a covalent compound with hydrogen at the beginning, it represents hydro Bromma acid. OK. So this is not an answer. The next one is also a covalent compound with a hydrogen in the beginning. So that's a dead giveaway that we have an acid. This one here is called tic acid. And then we have C and D, if we look at these two options, D is an acid because it is a covalent compound with a hydrogen at the beginning here, this is called hypo chorus acid. The answer is option C we have CNH together, we don't have the hydrogen in the front. Uh So, and it's covalent, but it doesn't have the hydrogen in the front. We said there are a few exceptions where hydrogen may not be in the front of the covalent compound such as acetic acid and positively charged AM means here ch four doesn't constitute one of those exceptions. So this would not represent a typical type of acid. So in this question, the answer is letter C.
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concept
Characteristics of Acids
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Now, we can say that acids belong to a distinct class of co compounds because of their characteristics in aqueous solutions. Now, here we can take a look at dissolution, taste reactivity and how acids react with litmus paper when it comes to dissolution, we're going to say that they ionize into hydrogen or hydro ions. Hydrogen ions are H plus hydro ions are H 30 plus these two things are interchangeable. Later on when we go into further discussions of how acids react within aqueous environments, we'll see why that's true. Now, here we're going to say the ionized to hydrogen ion or hydro ion and an anion when dissolved in a solvent, typically water. So, for example, here we have hydrochloric acid. When it dissolves into its ions, it gives us H plus ion aqueous plus C minus aqueous. And then here we have sulfuric acid. If we were to just completely ionize it where it gives off all of its H plus ions, we'd have two H plus ions aqueous plus our sulfate ion aqueous. Later on, we'll see that this doesn't really happen when it, when you, your acid has multiple H plus ions, they actually are lost within steps. Right now. We're not going into that detail. Just realize that if we were to just remove all the H pluses in this particular example, we'd have two H pluses at the end. Now, here for taste, we're gonna say the presence of H plus or H three plus ions give acids a sour taste. So if you want to think about sour, think of citrus fruit, we have lemons, we have oranges, they kind of have a sour taste to them. Now, their reactivity, we're gonna say they react with metals to form H two gas. A very common type of experiment that some of you may have done in lab is the reaction between hydrochloric acid and magnesium solid. Here. When we do this, we produce hydrogen gas plus magnesium chloride, aqueous here. Let's not worry about balancing the equation. Just realize that we create these two things as products. And finally litmus paper, we're gonna say litmus paper is a type of paper that changes colors and respond to an acid or a base for an acid. It changes red litmus paper or it changes blue litmus paper into red. So we take our blue litmus paper, dip it within an acidic solution. And when we pull it out, the blue litmus paper has changed to red. So these are some of the most important characteristics of a typical acid
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example
Acids Introduction Example
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Here in this example, question, it says sulfuric acid is added to a large container of water. How is the solution different from the original water? All right. So here the solution has fewer hydrogen ions. Now, remember when we place sulfuric acid within our aqueous solution, it will produce H plus ions plus sulfate ions. Again, this doesn't all happen in one, in one step. We'd lose each H plus ions within different steps. We'll talk about that much later on. But for right now, if we were to lose all the H plus ions, we'd have two H plus ions within solution and then our sulfate ion and solution. So there should be more H plus ions within our solution. Not fewer. The solution turns blue litmus paper red, which is true. The solution turns red, litmus paper blue, no, an acid would change blue litmus paper into red. The solution has more water molecules. So here molecules would mean that it stays intact. It doesn't become ions. But we know that if we take sulfuric acid and place it within the water, we're gonna produce these ions. So there would be fewer molecules and more ions within our new solution. So here, the only answer that's true is option B.
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Problem
Problem
Which of the following is true in regards to HNO3?
a) It has a bitter taste. b) It produces H+ ions in water.
c) It exists as only molecules when dissolved in H2O. d) It decreases the acidity of the solution.
A
It has a bitter taste.
B
It produces H+ ions in water.
C
It exists as only molecules when dissolved in H2O.
D
It decreases the acidity of the solution.
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