Question

Write the net ionic equation for the reaction between solutions of: (a) Aluminum nitrate and sodium hydroxide (b) Potassium phosphate and calcium chloride (c) Magnesium sulfate and sodium carbonate

Short answer

The net ionic equations for the reactions are: (a) \(Al^{3+} (aq) + 3OH^{-} (aq) \rightarrow Al(OH)_{3} (s)\) (b) \(2PO_{4}^{3-} (aq) + 3Ca^{2+} (aq) \rightarrow Ca_{3}(PO_{4})_{2} (s)\) (c) \(Mg^{2+} (aq) + CO_{3}^{2-} (aq) \rightarrow MgCO_{3} (s)\)

Step-by-step solution

Write the balanced molecular equation

Write the balanced molecular equation for the reaction between aluminum nitrate (Al(NO₃)₃) and sodium hydroxide (NaOH). Al(NO₃)₃ (aq) + 3NaOH (aq) → Al(OH)₃ (s) + 3NaNO₃ (aq)

Write the balanced complete ionic equation

Now write the balanced complete ionic equation by breaking the solubles into their respective ions. Al³⁺ (aq) + 3NO₃⁻ (aq) + 3Na⁺ (aq) + 3OH⁻ (aq) → Al(OH)₃ (s) + 3Na⁺ (aq) + 3NO₃⁻ (aq)

Write the net ionic equation

Cancel out the spectator ions that don't participate in the reaction and simplify. Al³⁺ (aq) + 3OH⁻ (aq) → Al(OH)₃ (s) The net ionic equation for the reaction between aluminum nitrate and sodium hydroxide is: \(Al^{3+} (aq) + 3OH^{-} (aq) \rightarrow Al(OH)_{3} (s)\) #(b) Potassium phosphate and calcium chloride#

Write the balanced molecular equation

Write the balanced molecular equation for the reaction between potassium phosphate (K₃PO₄) and calcium chloride (CaCl₂). 2K₃PO₄ (aq) + 3CaCl₂ (aq) → Ca₃(PO₄)₂ (s) + 6KCl (aq)

Write the balanced complete ionic equation

Now write the balanced complete ionic equation by breaking the solubles into their respective ions. 6K⁺ (aq) + 2PO₄³⁻ (aq) + 3Ca²⁺ (aq) + 6Cl⁻ (aq) → Ca₃(PO₄)₂ (s) + 6K⁺ (aq) + 6Cl⁻ (aq)

Write the net ionic equation

Cancel out the spectator ions that don't participate in the reaction and simplify. 2PO₄³⁻ (aq) + 3Ca²⁺ (aq) → Ca₃(PO₄)₂ (s) The net ionic equation for the reaction between potassium phosphate and calcium chloride is: \(2PO_{4}^{3-} (aq) + 3Ca^{2+} (aq) \rightarrow Ca_{3}(PO_{4})_{2} (s)\) #(c) Magnesium sulfate and sodium carbonate#

Write the balanced molecular equation

Write the balanced molecular equation for the reaction between magnesium sulfate (MgSO₄) and sodium carbonate (Na₂CO₃). MgSO₄ (aq) + Na₂CO₃ (aq) → MgCO₃ (s) + Na₂SO₄ (aq)

Write the balanced complete ionic equation

Now write the balanced complete ionic equation by breaking the solubles into their respective ions. Mg²⁺ (aq) + SO₄²⁻ (aq) + 2Na⁺ (aq) + CO₃²⁻ (aq) → MgCO₃ (s) + 2Na⁺ (aq) + SO₄²⁻ (aq)

Write the net ionic equation

Cancel out the spectator ions that don't participate in the reaction and simplify. Mg²⁺ (aq) + CO₃²⁻ (aq) → MgCO₃ (s) The net ionic equation for the reaction between magnesium sulfate and sodium carbonate is: \(Mg^{2+} (aq) + CO_{3}^{2-} (aq) \rightarrow MgCO_{3} (s)\)

Key concepts

Chemical Reactions

Understanding chemical reactions is fundamental in chemistry. They involve the transformation of substances through the breaking and forming of chemical bonds. This process often results in the creation of new products with properties different from the reactants. For instance, when we mix solutions of aluminum nitrate and sodium hydroxide, a reaction occurs, leading to the formation of aluminum hydroxide and sodium nitrate.

During this process, the ions in the reactants rearrange, and only those that undergo a change appear in the net ionic equation—a streamlined version that focuses solely on the ions involved in the chemical change. This leaves out the spectator ions, which do not participate in the reaction, simplifying our understanding of the chemical process at hand.

Precipitation Reactions

A precipitation reaction is a type of chemical reaction where two soluble substances react in solution to form an insoluble solid called a precipitate. For example, when potassium phosphate and calcium chloride solutions are mixed, they undergo a precipitation reaction to form calcium phosphate, a solid, and potassium chloride in the solution.

The beauty of net ionic equations lies in their ability to show us the essence of these reactions: the formation of the precipitate. The equation for a precipitation reaction eliminates the spectator ions, highlighting the direct interaction between the ions that lead to the formation of the solid. This focus aids students in identifying the driving force behind these reactions and in predicting the outcomes of mixing various ionic compounds.

Solubility Rules

To predict whether a precipitation reaction will occur, we need to be familiar with solubility rules. These rules help us determine whether a substance will dissolve in water to form an aqueous solution or remain undissolved as a precipitate. When solutions of magnesium sulfate and sodium carbonate are combined, the solubility rules inform us that while most sulfate and carbonate salts are soluble, magnesium carbonate is not. Therefore, it precipitates out of the solution.

Students can use these rules as guidelines to write net ionic equations correctly: only insoluble substances appear as solids, while the soluble ones break apart into ions. By knowing these rules, students enhance their ability to predict reaction products and write accurate net ionic equations, a vital skill in the study of chemistry.