Is KBrO a weak base?

Question

I really need to know this (search KBrO on the internet and you get a bunch of radio stations!) Potassium Hypobromite is what I think it's called - just a simple problem, what's the pH of 0.200 M KBrO?

Ka = 2.0 x 10^(-9)

I can probably get it if I find out if KBrO is a weak base (or possibly a strong base) but, if anyone else wants to work it i sure wouldn't mind something to compare my answer with :)

Thanks! :)

Answer 1

here's a clue. if your given an Ka (which means there's a Kb) then yes it's either a weak base or weak acid

because things like HCl... you can't even find a Ka because it almost fully dissociates

KBrO ----> K+ and BrO-

BrO- + H2O < ------ > HBrO + OH-

.2M ............................ O M....... O M

-x .......................   ..... +x  ..........+x

.2-x  ......................  .... x  ............ x

find Kb ... 10^-14/Ka = Kb

Kb = [HBrO][OH]/[BrO-]

solve  for x

Kb= (x^2)/(.2-x)

once you find x, that is also your OH concentration

-log [OH]= pOH

14= pH + pOH

pH = 14-pOH

sorry i don't have anyway of calculating that for your at the moment, but good luck

Answer 2

A solution of KBrO is basic.  We can predict that because it contains the cation of a strong base and anion of a weak acid, HOBr (or HBrO).

It looks like you are telling us that HOBr has a Ka of 2.0 x 10^-9.  If that's the case, then OBr- has a Kb of Kw/Ka or 5.0 x 10^-6.

OBr- + HOH <==> HOBr + OH-

Kb = [OH-] [HOBr] / [OBr-]

Kb = x^2 / 0.200 = 5.0 x 10^-6

solve for x

x = 1.0 x 10^-3 = [OH-]

pOH = 3.00

pH = 14.00 - pOH = 11.00