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WCLN - Weak Acids - Chemistry

Defines weak acids and gives some examples. Examines and explains the conductivity of weak acids solutions. Shows how to use the acid table to identify and compare predicted conductivities of weak acids. Examines trends in acid strength, degree of ionization, and acid ionization constant (Ka) as shown on the acid table. http://www.BCLearningNetwork.com. 0:01acids and bases can be classified 0:04as either strong or weak here it will deal with weak acids 0:07weak acid is an asset that is less than a hundred percent 0:11ionized in a clear solution an example of a weak acid 0:15is acidic acid CH 3 COOH 0:18it reacts with water to produce a hydrazone in mind 0:23and an acetate or it anyway and I'm unlike strong acids which I a nice to 0:29completion 0:30weak acids exist as equilibrium mixtures as shown by the double arrow 0:34promos to the weak acids dealt with in chemistry 12 0:38the molecular form is highly favored at equilibrium 0:42and the concentrations at the in's are very low compared to that of the 0:46molecules 0:47so a solution to the scenic acid consists mostly of mutual 0:51CH 3 COOH molecules and the concentrations at the in's 0:56in this solution her very low if we insert a conductivity apparatus into 1:01pure water 1:02it is not conduct enough to make the ball claw now will add some acidic asset 1:08to the water 1:08you see dick acid molecules spread out to fill the solution 1:14a small number obviously took acid molecules Inis 1:18and the ball close to me because there's a small number by its present in the 1:24solution a weak acid 1:25the conductivity is not zero but it is low 1:28so weak acids that start out as neutral molecules 1:33make CH 3 COOH are weak electrolyte 1:37so now that we know what we Cassens are 1:40where do we find them you may recall that the six acid in the top left in the 1:44ass a table 1:46are classified as strong acids remember these are 100 percent 1:50ionized in a quiz solution species below high drawing him on the lapd 1:56all the way down to water can act is weak acids 1:59somebody's including water around the protec- 2:02so they can also act as weak bases as we'll see later 2:06just a quick word about the two species on the very bottom at the last side 2:11hydroxide and ammonia these cannot 2:14actors acids in a quiz solution they're found on the right side the ass a table 2:19and are classified as bases the only reason they're written here 2:24is that they happen to be conjugate acids at the base is old two-minus 2:28and NH two-minus noticed they both have a single arrow pointing toward them 2:36which is further verification that these are not assets 2:39these reactions go only in reber's not for 2:43looking at the weak acids it's important to understand 2:47that they get progressively weaker as we go down the left side of the table 2:51from a child 3 th to all because assets get weaker as we move down the table 2:58we can also say that the degree a vine is Asian decreases 3:01this is indicated by the fact that the deluge that there I nyse: Asian constant 3:07k 3:08get smaller as we move down the table take a look at these two verify dissed 3:13yourself 3:13of course we can also say 3:17that weak ass its progressively get stronger as we move 3:20up on the left side from water at the bottom a child 3 at the top 3:25this means the degree a binarization increases 3:29as we move up 3:31and a game this is reflected by the increase in k values 3:34as we move out 3:36molecular weak acids are indicated here by the red arrows 3:41these are assets that are neutral molecules before the I night 3:45because the degree a binarization decreases as we move down the table 3:50it means that the number of dissolved ions present in one molar solutions are 3:54these molecular acids 3:56will decrease as we move down 3:59so what do you think the trend and conductivity molecular assets will be 4:03as we move down the column 4:07electrical conductivity depends on the number of dissolved ions in solution 4:11so as we move down the column and the number of dissolved ions decreases 4:17conductivity of molecular acids also decreases 4:21so if we were to compare the conductivity of phosphoric acid 4:25without a boric acid we would predict that phosphoric acid has higher 4:30conductivity 4:31and boric acid we can also see that higher conductivity 4:35correlates with a higher value for the ionization constant 4:38K 4:40noticed that many of the species that act is weak acids 4:43orion's to begin with 4:45as expected the ability and featured these to act as an acid 4:50decreases as we move down the left side of the table 4:54this is reflected by a decrease in there K values 4:57as we move down 4:59because these are I ins they do not occur as substances themselves in nature 5:04if it's in an in- it would need to be have an accompanying cat I'm 5:08and if it's a cat I N it would need to have an accompanying an A 5:13for example the HSR for minus I N could be accompanied by the spectator katayan