3.1.4 Qualitative Analysis

Question 1

What are the two stages when testing for carbonate and the equations to go with them

Answer 1

First add acid to produce a gas from the solid.
XCO3 + H2SO4 —> CO2 + H2O

Bubble the gas through lime water if it goes cloudy CO2 is present.
CO2 + Ca(OH)2 —> CaCO3 + H2O

Question 2

What are the 2 stages of testing for sulfates with the equation

Answer 2

First add hydrochloric acid
Then barium chloride, if a white precipitate form sulfate are present.
Ba^2+ + SO4^2- —> BaSO4

Question 3

How to test for halides

Answer 3

First dissolve the solution in an acid.
Then add silver nitrate (AgNO3)
A white to cream precipitate will form depending on the halide.
To find the exact halide add dilute ammonia. If it dissolves then it is chlorine.
Then add concentrated ammonia. If it dissolves it’s bromine.
If it doesn’t dissolve its iodine.

Question 4

How to test for ammonium

Answer 4

Add warm sodium hydroxide to the substance.
If Ammonium is present then ammonia gas will be given off which has a distinct smell and will turn red litmus blue.