00:01
Okay, so here we have a reaction, a plus 2b is an equilibrium with c.
00:11
And so we have what we start out with 2 moles of a and 3 moles of b, and in a 6 -liter container.
00:18
And so question 21, at equilibrium, the concentration of a is 0 .3 moles per liter, and we want to know what the concentration of b is at equilibrium.
00:27
So first let's set up an ice table, so we can get our equilibrium expression.
00:32
So a, we're starting out with 2 moles over 6 liters.
00:38
So 2 over 6 is 0 .333 molar.
00:43
And then for b, it's 3 moles in 6 liters.
00:47
So that would be 0 .50.
00:50
And then we're starting out with 0 of c.
00:52
Then the change minus x for a, minus 2x for b, because of our two coefficient here, and then plus x for c.
01:01
So at equilibrium, a is going to be 0 .333 minus x.
01:11
B will be 0 .50 minus 2x, and c will be x.
01:17
So we know a at equilibrium is 0 .3 .0.
01:26
And that's going to be equal to this value, because they're both at equilibrium, so they should be the same.
01:33
We also know b at equilibrium is 0 .50 minus 2x.
01:44
And we want to know what the concentration of b is...