Hard Water often contains calcium chloride. The calcium ion in solution can be detected using a solution of sodium phosphate. When a solution of calcium chloride is mixed with a solution of sodium phosphate, a precipitate forms.
a. What is the chemical name for the precipitate that forms when solutions of calcium chloride and sodium phosphate are mixed?
b. Write a net ionic equation representing the reaction that occurs when solutions of calcium chloride and sodium phosphate are mixed.
c. List all spectator ions that are present when solutions of calcium chloride and sodium phosphate are mixed.
a. The chemical name for the precipitate that forms when solutions of calcium chloride and sodium phosphate are mixed is calcium phosphate.
b. To write the net ionic equation, we need to first write the balanced chemical equation for the reaction. The balanced chemical equation is:
3CaCl2 + 2Na3PO4 -> Ca3(PO4)2 + 6NaCl
From this balanced chemical equation, we can identify the ions that participate in the reaction. These ions are:
Ca2+ from CaCl2
PO43- from Na3PO4
The net ionic equation shows only the ions that participate in the reaction and excludes the spectator ions. So, the net ionic equation for this reaction is:
3Ca2+ + 2PO43- -> Ca3(PO4)2
c. Spectator ions are ions that are present in the reaction mixture but do not participate in the reaction itself. In this case, the spectator ions are:
Na+ from Na3PO4
Cl- from CaCl2
These ions remain in solution unchanged and do not react with each other or affect the formation of the precipitate.
a. calcium phosphate
b. molecular equation:
3CaCl2 + 2Na3PO4 ==> Ca3(PO4)2 + 6NaCl
total ionic equation (with phases) aq for aqueous, s for solid:
3Ca^2(aq) + 6Cl^-(aq) + 6Na^+(aq) + 2[PO4]^3-(aq) ==> Ca3(PO4)2(s) + 6Na^+(aq) + 6Cl^-(aq)
net ionic equation:
3Ca^2(aq) + 2[PO4]^3-(aq) ==> Ca3(PO4)2(s)
c. The spectator ions are those ions in the TOTAL ionic equation above (which the problem didn't ask for) that are NOT in the net ionic equation. Those are the Na^+ and Cl^-