Question

which reaction best represents the correct net ionic equation for the reaction of calcium nitrate with potassium phosphate?
ca²⁺(aq) + po₄³⁻(aq) → capo₄(s)
ca²⁺(aq) + 2no₃⁻(aq) → ca(no₃)₂(aq)
k⁺(aq) + no₃⁻(aq) → kno₃(aq)
2ca²⁺(aq) + 3po₄³⁻(aq) → ca₂(po₄)₃(s)
3ca²⁺(aq) + 2po₄³⁻(aq) → ca₃(po₄)₂(s)

Explanation:

Step1: Write the chemical formulas

Calcium nitrate is \(Ca(NO_3)_2\), which dissociates into \(Ca^{2 + }\) and \(NO_3^-\) ions. Potassium phosphate is \(K_3PO_4\), which dissociates into \(K^+\) and \(PO_4^{3 - }\) ions.

Step2: Write the balanced molecular equation

\(3Ca(NO_3)_2(aq)+2K_3PO_4(aq)
ightarrow Ca_3(PO_4)_2(s)+6KNO_3(aq)\)

Step3: Write the total ionic equation

\(3Ca^{2 + }(aq)+6NO_3^-(aq)+6K^+(aq)+2PO_4^{3 - }(aq)
ightarrow Ca_3(PO_4)_2(s)+6K^+(aq)+6NO_3^-(aq)\)

Step4: Cancel out the spectator ions (\(K^+\) and \(NO_3^-\))

The net - ionic equation is \(3Ca^{2 + }(aq)+2PO_4^{3 - }(aq)
ightarrow Ca_3(PO_4)_2(s)\)

Answer:

\(3Ca^{2 + }(aq)+2PO_4^{3 - }(aq)
ightarrow Ca_3(PO_4)_2(s)\) (the last option)