[annelise]

I have been set this question:

MHSO4 (where M stands for either Na or K) is a crystalline solid that dissolves in water giving a solution containing M⁺, HSO_4-, H⁺ and SO₄^2- ions.

Describe a chemical test (apart from indicators) by which you could demonstrate that an aqueous solution of MHSO₄ is acidic.

So far I got that 1 test could be to test for CO2 by bubbling it through limewater (i.e. CO2 turns limewater milky in appearance), and I have this equation involving for that reaction:

CO2 (g) + Ca(OH)2 (aq) ---- CaCO3 (s) + H2O(l)

and the ionic half equation for testing for CO2 involving the H+ ions from the acid salt is:

2H+ (aq) + CO3- (s) ----H2O (l) + CO2 (g)

BUT I DON'T UNDERSTAND WHERE YOU SAY THE CARBON COMES INTO IT ALL? IS IT JUST FROM THE ATMOSPHERE? I AM CONFUSED ABOUT HOW TO WRITE THE EQUATION SAYING IS MHSO4 IS DISSOLVED IN WATER IT PRODUCES M+, HSO4-, H+ AND SO4(2-) IONS AND THEN INCORPORATING THE WHOLE C02 THING!

IM GETTING TOTALLY CONFUSED!

[Donaldson Tan]

you need a test to show the presence of hydrogen ions in the solution. addition of solid carbonate. eg. magnesium carbonate, will yield carbon dioxide gas, if H+ is indeed present.

calcium carbonate not good for use, because the insoluble calcium sulphate formed will coat the unreacted calcium carbonate and thus prevent furthur effervescence of carbon dioxide gas. In situation whereby [H+] is low, you may not observe effervescence because so little carbonate has reacted due to formation of the coat.

[Mitch]

ph meter  

[annelise]

ok cool! Thank you!!!!!