00:01
Hi, over here we're going to calculate the percent of ionization of a solution which is going to have a 2 .50 molar concentration of hno2, which has a ka equal to 4 .6 times 10 to the minus 4.
00:19
So over here, the reaction that we're considering is hno2 plus water, which would produce h2o plus plus no2 minus.
00:31
Minus.
00:32
We're going to say that we have an initial concentration on our ice table of c0, which is going to be equal to the 2 .50 molar that is given to us in the problem.
00:43
Water is not going to enter equilibrium, and initially we're going to have zero for each of the components.
00:49
We're going to have a change of minus x plus x and plus x, respectively, multiplying the fraction that is is going to get ionized by the stoichiometric coefficient and thus at the equilibrium we're going to get c0 minus x, x and x.
01:05
So what we want to do is to solve for the value for x in this equation.
01:11
So in this case we're going to have the ka is going to be equal to the equilibrium concentration of h2o plus times the concentration of no2 minus divided by the concentration of hno2.
01:22
Remember that water is not going to enter since it is going to be a condensed phase and its activity is defined as 1.
01:31
So this is going to get equal to x squared divided by c0 minus x after replacing values that were given here.
01:39
And at the same time, this should be equal to 4 .6 times 10 to the minus 4.
01:43
So over here we have two options.
01:46
Option 1 is going to be to make the approximation of a small x, which is going to give us an approximate value for the percent of ionization.
02:01
In this case, the approximation is probably going to be good enough if we keep our result up to two significant digits...