00:01
It looks like you've got 13, 14, 16 right, so i assume that you needed help with just 15 and 17.
00:10
For 15, the ph is provided along with the concentration of hypobromous acid.
00:21
To calculate the ka value, we typically reference the ka equation, ka equals the hydronium concentration squared divided by the concentration of the acid minus hydronium.
00:38
A lot of times people will assume that this is negligible, so they'll get rid of it and then calculate accordingly, where the hydronium just ends up being the square root of ka times the weak acid concentration.
00:53
But i will retain it because it's still an easy calculation.
00:58
The hydronium concentration is 10 to the negative ph, so it'll be 10 to the negative 4 .17.
01:07
We'll square that and then divide by the concentration of the hypobromous acid, 0 .63, and then subtract off 10 to the negative 4 .17, and we get 7 .26.
01:25
Yeah, they must have times 10 to the negative 9.
01:34
So what they did is they got rid of this, and then they just did 10, no, because you still should get about the same answer, 4 .17 squared divided by 0 .63.
01:57
Probably going to get the exact same answer.
01:59
They probably did some rounding somewhere along the way...