Electrolytes - Video Tutorials & Practice Problems
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Electrolytes are compounds that can conduct electricity once they are dissolved in a solvent.
Understanding Electrolytes
Whenever you add a solute to a solvent there are three possible outcomes:the solute dissolves completely, dissolves partially or doesn't dissolve at all into ions.
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Categories of the Electrolytes
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Now electrolytes represent compounds that conduct electricity when entering their ionic forms when dissolved or melted. Now recall conductivity is a physical property that deals with the ability of electric current to flow through a material. Now, we have strong electrolytes, weak electrolytes, and non electrolytes. With strong electrolytes, we say they represent solutes that completely or totally dissolve into ions when placed in a solvent. So for example, let's say we had a b solid here. If there were a strong electrolyte it would break up 100% to give us a positive aqueous, when you are an ion in solution you're aqueous, plus b minus aqueous. We're gonna say strong electrolytes are strong acids, strong bases, and are soluble ionic compounds. Remember, we know our soluble ionic compounds from the solubility rules. Now, if we take a look here, let's look at our strong acids first. For strong acids, we classify them either as hallow acids, trioxide acids, or tetraoxide acids. So our hallow acids that are strong are hydrochloric acid, hydrobromic acid, and hydroiodic acid. Here if we look at the periodic table, we have our strong assets here. So we said that h c l is 1, h b r is 1, and HI is another. Trioxides mean they possess 3 oxygens, so chloric acid is HClO 3, hbr03, and h n o 3. So here notice that there's no h I o 3. H I o 3 does not constitute a strong acid. So here, h n o 3 would be a strong one, and then here we'd have hcl03, and then we have h b r o 3. And then here our tetra oxides have 4 oxygens involved, so this would be h c l o 4, perbromic acid is h b r o 4, periotic acid is h I o 4, and then finally sulfuric acid which is h two s o four. So placing them here on the periodic table we see the way that our strong acids shape different sections of the periodic table. So keep in mind these are all the strong acids that exist. For those of you who carry on into later, stronger, or like more difficult chemistries, these strong acids will make an appearance again. So keep them in mind when asked to discuss questions dealing with strong acids.
Strong Electrolytes break up into ions completely and are grouped into 3 categories:Strong Acids, Strong Bases and Soluble Ionic Compounds.
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Electrolytes Example 1
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Here it says, provide the equation when sulfuric acid dissolves in a solvent. Sulfuric acid is a strong acid, so if we're talking about its complete dissociation, we're going to say here h two s o four, and we're gonna break it up into its ions. It possesses 2 h plus aqueous ions, plus s 042 minuteus aqueous ion, sulfate ion. So here we'd say sulfuric acid will produce 2 h+aqueous++++. When we get into later chapters on acid and base chemistry, we'll learn further that this acid actually doesn't lose both hydrogens at the same time, h plus. It actually loses them in stages. But this early on in chemistry, just realize that overall, if this were to completely break up into ions, it would break up into 2 H+ ions and 1 Sulfate ion.
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Electrolytes Concept 2
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Here we're going to say when group 1 a and 2 a metals combined with the following anions, they form strong bases. So the anions include hydroxide ion, which is Oh minus, hydride ion, which is H minus, the amide ion, which is NH2 minuteus, and the oxide ion which is o two minus. The group 1a and 2a metals include, we're going to have here lithium, sodium, potassium, rubidium, and cesium. And then in group 2 a we're gonna have calcium, strontium, and barium. So it's just the ones that I've written in which will be the metals when they combine with these four negative ions, will create a strong base. So here, for hydroxide. So let's say I took lithium ion and hydroxide ion, and then I took calcium ion and hydroxide ion. So remember, with charges when the numbers are the same, they cancel out. So this would just be l I o h, lithium hydroxide. Here the numbers are different, there's a 2 here and a 1 here, so 2 would come here and 1 would come here. That 2 is for all of the calcium hydroxide all of the hydroxide ions, so that'd be c a o h 2. Hydride. So let's say I took n a+H minus. Here the numbers are the same so they just cancel out to give me n a h which is sodium hydride. Here let's say we had s r two+hminusone, So again the numbers are different. When they're different they crisscross, so 2 from here would come here and 1 from here would come here to give me strontium hydride. Then we have amide ion, so let's say we did potassium with n h two minus, that would give me potassium amide. Here we have Barium with the amide ion. The numbers are different, so 2 would come here and one would come here. So this would be Barium Amide, so b a n h two parenthesis 2. And then we have oxide, so let's say we did c s+in0twominus. The numbers are different, so what happens they crisscross, one comes here, 2 comes here, so this would be c s 2 o, cesium oxide. And then let's say we had c a 2+ and o two minus here. The numbers are the same, so they don't crisscross, they just out. So calcium oxide. So here we're just looking at different combinations of the metals that I have from groups 1 a and 2 a in blue, mixed with one of these negative ions. Doing that will form a strong base. Remember, as a result of being a strong base, you are a strong electrolyte.
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Problem
Problem
Which of the following represents a strong base?
A
Mg(OH)2
B
CH4
C
H2
D
CsH
E
CaOH
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concept
Electrolytes Concept 3
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Here we're going to say that weak electrolytes represent solutes that partially dissolve into ions when placed into sol solvent. So here we have a b solid. To show that it's a weak electrolyte, we use double sided arrows to show that not all of a b dissolves into ions. So he would get a+aqueousplusbminusaqueous. Very little of these ions would actually be forming because again it's a weak electrolyte. We're gonna say here that weak electrolytes are either weak acids or weak bases. Now, for weak acids, if an acid is not strong, then it is automatically going to be weak. So the strong acids that we examined earlier are the strong acids acids you need to remember. If you see an acid and it's not one of those that we discussed, by default it is a weak acid and therefore it is a weak electrolyte.
Weak Electrolytes partially break up into ions and are grouped into 2 categories: Weak Acids and Weak Bases.
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example
Electrolytes Example 2
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Here it says, which of the following represents a weak binary acid and therefore a weak electrolyte? So remember, a binary acid does not possess oxygen. Oxygen. So automatically all the ones with oxygen are out. So we have HCl and HCN. So they both represent binary acids because of the lack of oxygen, but the one that's a weak electrolyte would have to be the one that is also a weak acid. HCl is one of our strong acids, so it would be a strong electrolyte. So by default, HCN, which is hydrocyanic acid, would be our weak binary acid and therefore our weak electrolyte.
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Electrolytes Concept 4
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So now weak basis. We call these patterns for identification, so they're a little bit different. So we're gonna have to just memorize them. Here we're gonna say weak bases include from group 2 a, beryllium hydroxide and magnesium hydroxide, and then also we have ammonium hydroxide or neutral amines. Now what exactly is an amine? Well, an amine is a compound that contains only nitrogen and hydrogen. For example, ammonia is an amine which is n h 3, and an amine could be a compound that contains carbon, nitrogen, and hydrogen. So an example here would be methylamine, which is c h three n h two. So these are two examples of amines. They can have either just nitrogen and hydrogen or carbon, nitrogen and hydrogen. Now for non electrolytes, these don't break up at all when put into a into a solvent. So they consist of molecular slash covalent compounds, so those are interchangeable, that, never dissolve into ions. So here we'd have a b solid and when I throw it into water it becomes surrounded by the water so we'd say a b aqueous. Now non electrolytes include water, sugars, and alcohols. So sugars are compounds with the molecular formula of cnh2nh20n. So glucose is an example of this because it's c 6 h 1206. Sucrose is also a sugar. It doesn't fit this formula exactly as nicely but it's c 12 h 22 o 11. So with sugars at this point, these are the 2 most common ones that you would see. Alcohols on the other hand are covalent compounds with c and h connected to o h. So methanol is CH3 connected to o h, and phenol is c 6h5 connected to o h. So in both they have carbon and hydrogen in the beginning and then they have the o h following it up. Okay. So then the o h here at the end. So again, water, sugars, and alcohols constitute non electrolytes. They don't break up at all within our solvent.
Non-Electrolytes do NOT break up into ions at all and are commonly referred to as molecular compounds.
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Problem
Problem
Which of the following represents a non-electrolyte?
A
(CH3)2NH2
B
NaOH
C
HIO3
D
C2H5OH
E
CsNH2
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Problem
Problem
Each of the following reactions depicts a solute dissolving in water. Classify each solute as a strong electrolyte, a weak electrolyte or a non-electrolyte.
a) PbSO4 (s) → PbSO4 (aq)
b) HC2H3O2 (aq) ⇌ H+ (aq) + C2H3O2− (aq)
c) CaS (s) → Ca2+ (aq) + S2− (aq)
d) Hg (l) → Hg (aq)
A
a) non-electrolyte; b) strong electrolyte; c) strong electrolyte; d) non-electrolyte
B
a) non-electrolyte; b) weak electrolyte; c) strong electrolyte; d) non-electrolyte
C
a) non-electrolyte; b) weak electrolyte; c) weak electrolyte; d) non-electrolyte
D
a) weak electrolyte; b) strong electrolyte; c) strong electrolyte; d) non-electrolyte
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Problem
Problem
Which of the following statements is true?
A
Perbromic acid, HBrO4, represents a weak electrolyte
B
Lithium chloride, LiCl, represents a non-electrolyte
C
Formic acid, HCO2H, represents a strong electrolyte
D
Zinc Bromide, ZnBr2, represents a strong electrolyte