So we will use minuses here because that's how much

of the sodium chromate will dissolve.

That's the molar solubility.

I will add 2s here.

I will add s over here.

That will still give me some solid in solution, I mean in the container,

I have 2s for that, and I have 2.6 x 10 to the minus 3 plus s for this.

Now, I will always want to write the Ksp expression it's

the silver ion concentration squared.

I'm looking at the reaction, I'm doing the powers a lot of times students try to skip

this step to save time, but

then they invariably forget to work with those coefficients.

Then I will look at the silver concentration, and that was 2s, and

it's squared, and then I will look at the chromate concentration, which I see here,

2.6 times 10 to the minus 3 plus s, so all of this is multiplied.

Now we're going to assume that S is very small compared to the other values,

and ignore this term for simplicity sake.

We'll make sure we go back and check that it was a valid assumption.

So all of this is going to be equal to the number

of ksp which is given in the problem.

1.2 times 10 to the minus 12.

And so I will multiply the 2 times 2 that will be 2 squared and

then I'm going to multiply that to the 2.6 x 10 to the -3.

And that is going to give me 1.04 times 10 to the minus 2 times s squared.

So then I will divide both sides by the 1.04 times 10 to the minus 2,