Solubility rules compounds containing group 1 alkali metals or ammonium (nh4+) are soluble. nitrates (no3−), chlorates (clo3−), perchlorates (clo4−), and acetates (c2h3o2−) are soluble. chlorides (cl−), bromides (br−), and iodides (i−) are soluble, except for compounds containing silver (ag+), mercury(i) (hg22+), and lead (pb2+). sulfates (so42−) are soluble, except for compounds containing calcium (ca2+), strontium (sr2+), barium (ba2+), and lead (pb2+). hydroxides (oh−), carbonates (co32−), and phosphates (po43−) are insoluble, except for compounds containing group 1 alkali metals and ammonium (nh4+). sulfides (s2−) are insoluble, except for compounds containing group 1 alkali metals, ammonium (nh4+), magnesium (mg2+), calcium (ca2+), strontium (sr2+), and barium (ba2+).

All column 1 and Ammonium ion are soluble. That lets out A

Rule 1 says the nitrates are all soluble. That eliminates B

All column 1 compounds are soluble. That does C in. (C is Not the answer).

D is very nasty. You don't have any way to eliminate it. But two metals as reactive as K and Ba won't combine by ionization. In fact they shouldn't combine at all. D is incorrect.

E is the answer. All Sulfates react with any metal except a couple. Ba+2 is one of the exceptions.

E  

it means there are 3 atoms of oxygen

the correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.