Chemical Tests

Question 1

What are the reactants, conditions, and observations of a Carbonate test?

Answer 1

Add dilute nitric acid
Observe bubbles (can be hard to see)
Bubble the released gas through lime water to confirm it is a carbonate (it goes cloudy)
CO3(2-)(aq) + 2HNO3(aq) -> 2NO3(-)(aq) + CO2(g) + H2O(l)

Question 2

What are the reactants, conditions, and observations of a Sulfate test?

Answer 2

Add barium nitrate
See white ppt of BaSO4(s) if SO4 is present in the solution
Ba(2+)(aq) + SO4(2-)(aq) -> BaSO4(s)

Question 3

What are the reactants, conditions, and observations of a Halide test?

Answer 3

Add silver nitrate, get ppt if halide is present
Ensure identity by adding aqueous ammonia, and see which ppt dissolve
Cl - white ppt; dissolves in dilute NH3
Br - cream ppt; dissolves in conc NH3
I - yellow ppt; does not dissolve in conc NH3

Question 4

What are the reactants, conditions, and observations of an Ammonium test?

Answer 4

Heat with aqueous hydroxide, which forms NH3(g)
Damp litmus paper turns blue when held over the test tude - this confirms present of NH3(g)
NH4(+)(aq) + OH(-)(aq) -> NH3(g) + H2O(l)