00:01
All right, so here we need to find the ph range of the indicator.
00:07
I've given us a little equation here, if it will help a little bit.
00:13
But the k .a.
00:16
That we were given equals 3 .5 times 10 to the negative 9th.
00:25
So, we can use this equation here, which is the ka.
00:36
And the concentration of hydronium times a concentration of...
00:45
So it's basically the right side of the chemical equation here on top of the left side.
00:55
And since h2o is a liquid, we don't count it in this.
01:00
So we just use the h, the concentration of h -i -n.
01:05
Okay.
01:06
And we can rearrange that equation here so that it is h3o plus over ka equals chian over i -n minus.
01:39
And we know that when this concentration right here is 10 over 1 or 1 over 10, then that's when the indicator changes colors.
01:56
And so we can see its ph range here by that ratio.
02:03
So we can go down just a little bit here, and we'll plug the numbers into the equation.
02:10
So concentration of hydronium over 3 .5 times 10 to the negative 9th equals 10...