00:01
To calculate the percent ionization of this acid at such a low concentration and a moderately large k -a value, we're going to need to use the quadratic formula, where ka.
00:13
1 .3 times 10 to the negative 5, is going to be equal to the hydrogenium concentration squared, divided by the concentration of propionic acid, 0 .00800 minus the hydronium concentration.
00:34
Using the quadratic formula or your calculator or excel or mathematica or whatever your instructor has asked you to do, we'll solve for the hydronium concentration.
00:46
And we get a hydronium concentration of 3 .16 times 10 to the negative 4 molar.
00:54
So percent ionization is going to be equal to the degree to which it's ionized as represented by the hydronium ion, 3 .16 times 10 to the negative 4, divided by the original concentration .00800 times 100.
01:23
And we get, looks like we probably didn't need to use the quadratic formula, because it's not greater than 5 percent, but we get 3 .95 % ionized.
01:37
If we didn't use the quadratic formula, then the hydrogen concentration could be calculated, assuming this is small with respect to 0 .008, by rearranging it to get the square root of 1 .3 times 10 to the negative 5 times 0 .008.
02:01
This gives us 3.
02:10
0 .22 times 10 to the negative 4 and a percent ionization of 3 .22, 10 to the negative 4 divided by 0 .008 is 100.
02:37
We get 4 .03 percent ionized.
02:43
So to two significant figures, it's 4 .0 percent ionized...
