Q7 Dr Entropy Has A Water Sample Containing Both Phosphate And Sulfate And The Five Solutions


Q7. Dr Entropy has a water sample containing both phosphate and sulfate, and the five solutions

shown here:

  • sodium chloride, NaCl
  • iron(III) nitrate, Fe(NO3)3
  • calcium nitrate,
  • potassium hydroxide, KOH
  • ammonium fluoride, NH4F

(i) Explain how the two anions (phosphate and sulfate) could be separated making use of the solutions above and an equipment like a Büchner funnel that can collect precipitated solids on a filter while allowing the remaining solution to pass through into a flask.

(Hint: Refer to the solubility table at the end of this document to determine what could be added to precipitate only one of the two anions.)

(ii) In your answer show balanced chemical reaction equation for any relevant precipitation reaction, including the states of all chemical species.


Solubility table
Nitrates (NO3)
With all cations
Sodium (Na+)
With all anions
Potassium (K+)
With all anions
Ammonium (NH4+)
With all anions
Chlorides, lodides and
Bromides (CI-, I-, Br)
With most cations, except…
Ag+, Pb2+, Hg+
Chlorate CIO4
With all cations
Acetate (CH=COO-)
With almost all cations except…
CH,COOAg (sparingly)
Nat, K+ NH4+
Hydroxide (OH-)
With all other cations
Ca2+, Ba2+, Sr2+, Mg2+ (sparingly)
Nat, K* NH4+
Sulfide ($2-)
Ca2+, Ba2+, Sr2+, Mg2+
With all other cations
Carbonates (CO32-)
Nat, K* NH4+
With all other cations
Phosphates (PO43-)
Nat, K+ NH4+
With all other cations
Sulfate (SO42-)
With most cations except…
Ag+, Cal+, Ba?+, Sr2+, Hg*, Pb2+Science