Here it says consider the titration of 100 mills of 0.500 molar hydrobromic acid solution with 120 MLS of 0.450 molar potassium hydroxide solution. Which species would be an excess? All right, so there's two ways we can approach this question. One way is we could figure out what the equivalence volume of our titrate will be. So let's say I made this the titrate. Then we can say that M⁢acid⁢times⁢V⁢acid=⁢M⁢base⁢times⁢V⁢base, and we could calculate the volume of our base to reach the equivalence point.

If the volume we calculated is less than this, and that means Koh is an excess because we've gone beyond our equivalence volume. So let's just do it that way. Then we're going to look at another way we can approach the same question. So here we say we have 500 molar of hydrochromic acid and then 100 MLS. Then we have 0.450 molar of potassium hydroxide, and we're looking for its equivalence volume. Divide both sides by 0.450 molar and we get our equivalent volume for our strong baits as being 11.1 milliliters.

So that's how much strong base we need to add to get to the equivalence point. We have a volume that's even greater than that, which would mean that Koh would be in excess. So Koh is our species. That will be in essence. Another way we could attempt this question is to remember that moles equals leader times molarity. If we divide both these volumes by 1000, we get liters of each of means multiply, so I've multiplied them by their molarities.

Doing this would give me 0.500 moles of HBR and then multiplying the leaders times molarity of this would give me 0.0540 moles of Koh. This is also telling me that, hey, we have more Koh than HBR, more moles. So Koh again would be in excess. So again, two different ways you can approach this type of question. If they're asking you to figure out which one is an access, but they're giving you the volumes of both and the molarity of both, make either one of the tight print and then try to figure out its equivalence volume.

If the equivalence volume you calculated is lower than what they're giving to you, then you're in excess. You could also calculate the moles of each which everyone has. Greater moles would be the one in excess, right. So take those two approaches, you'll find the answer. In this particular case, the answer is option B.