Question

Write a net ionic equation for any precipitation reaction that occurs when \(0.1 \mathrm{M}\) solutions of the following are mixed. (a) zinc nitrate and nickel(II) chloride (b) potassium phosphate and calcium nitrate (c) sodium hydroxide and zinc nitrate (d) iron(III) nitrate and barium hydroxide

Short answer

a) Zinc nitrate and nickel(II) chloride b) Potassium phosphate and calcium nitrate c) Sodium hydroxide and zinc nitrate d) Iron(III) nitrate and barium hydroxide Answer: a) No precipitation occurs in this reaction. b) 2PO4^3- + 3Ca^2+ -> Ca3(PO4)2 (s) c) 2OH- + Zn^2+ -> Zn(OH)2 (s) d) 3OH- + Fe^3+ -> Fe(OH)3 (s)

Step-by-step solution

(a) Write the balanced chemical equation for zinc nitrate and nickel(II) chloride

Write a balanced chemical equation for the reaction between zinc nitrate (Zn(NO3)2) and nickel(II) chloride (NiCl2): Zn(NO3)2 + NiCl2 -> ZnCl2 + Ni(NO3)2 This equation tells us that zinc nitrate reacts with nickel(II) chloride to produce zinc chloride and nickel(II) nitrate.

(a) Identify the precipitate

Check the solubility rules for the products to determine if there is any precipitate. Both ZnCl2 and Ni(NO3)2 are soluble salts (as all nitrates and most chlorides are soluble), so there is no precipitation in this reaction.

(b) Write the balanced chemical equation for potassium phosphate and calcium nitrate

Write a balanced chemical equation for the reaction between potassium phosphate (K3PO4) and calcium nitrate (Ca(NO3)2): 2K3PO4 + 3Ca(NO3)2 -> 6KNO3 + Ca3(PO4)2 This equation tells us that potassium phosphate reacts with calcium nitrate to produce potassium nitrate and calcium phosphate.

(b) Identify the precipitate and write the net ionic equation

Check the solubility rules for the products to determine if there is any precipitate. Potassium nitrate is soluble, but calcium phosphate is insoluble. Therefore, calcium phosphate is the precipitate that forms in this reaction. To write the net ionic equation, we only need to include the ions involved in the formation of the precipitate: 2PO4^3- + 3Ca^2+ -> Ca3(PO4)2 (s)

(c) Write the balanced chemical equation for sodium hydroxide and zinc nitrate

Write a balanced chemical equation for the reaction between sodium hydroxide (NaOH) and zinc nitrate (Zn(NO3)2): 2NaOH + Zn(NO3)2 -> 2NaNO3 + Zn(OH)2 This equation tells us that sodium hydroxide reacts with zinc nitrate to produce sodium nitrate and zinc hydroxide.

(c) Identify the precipitate and write the net ionic equation

Check the solubility rules for the products to determine if there is any precipitate. Sodium nitrate is soluble, but zinc hydroxide is insoluble. Therefore, zinc hydroxide is the precipitate that forms in this reaction. To write the net ionic equation, we only need to include the ions involved in the formation of the precipitate: 2OH- + Zn^2+ -> Zn(OH)2 (s)

(d) Write the balanced chemical equation for iron(III) nitrate and barium hydroxide

Write a balanced chemical equation for the reaction between iron(III) nitrate (Fe(NO3)3) and barium hydroxide (Ba(OH)2): Fe(NO3)3 + 3Ba(OH)2 -> 3Ba(NO3)2 + Fe(OH)3 This equation tells us that iron(III) nitrate reacts with barium hydroxide to produce barium nitrate and iron(III) hydroxide.

(d) Identify the precipitate and write the net ionic equation

Check the solubility rules for the products to determine if there is any precipitate. Barium nitrate is soluble, but iron(III) hydroxide is insoluble. Therefore, iron(III) hydroxide is the precipitate that forms in this reaction. To write the net ionic equation, we only need to include the ions involved in the formation of the precipitate: 3OH- + Fe^3+ -> Fe(OH)3 (s)

Key concepts

Solubility Rules

Understanding solubility rules is crucial when predicting whether a precipitation reaction will occur. Solubility rules are guidelines that help determine whether a given ionic compound will dissolve in water. These guidelines tell us that compounds containing certain cations and anions are generally soluble in water. For instance, nitrates (NO_3^-) and most chlorides (Cl^-), with important exceptions like silver chloride (AgCl), are usually soluble. Conversely, compounds like calcium phosphate (Ca_3(PO_4)_2) and iron(III) hydroxide (Fe(OH)_3) are not soluble in water, forming an insoluble precipitate.

When mixing solutions, you can refer to these rules to predict whether or not a precipitate will form. For instance, while potassium nitrate (KNO_3) remains dissolved in solution due to its high solubility, calcium phosphate comes out of solution as a solid precipitate. Being able to determine the solubility of compounds helps streamline the process of writing net ionic equations, since only the reaction between ions that form the precipitate needs to be considered.

Chemical Equation Balancing

Balancing chemical equations is a fundamental skill in chemistry that ensures the law of conservation of mass is respected. Each element must have the same number of atoms on both sides of the reaction equation. In the provided examples, equations for various precipitation reactions were balanced by ensuring that the number of atoms of each element was equal on the reactant and product sides. For instance, balancing the reaction between potassium phosphate (K_3PO_4) and calcium nitrate (Ca(NO_3)_2) requires you to have three calcium ions and two phosphate ions on each side to form solid calcium phosphate and soluble potassium nitrate. Notably, balancing equations effectively helps in correctly writing net ionic equations, which focus solely on the species that undergo change during the reaction.

Insoluble Precipitate Identification

Identification of an insoluble precipitate is an essential part of predicting and understanding precipitation reactions. A precipitate is an insoluble solid that forms when two ionic compounds react in solution. This solid falls out of the solution and can be identified using solubility rules. For example, in the case of sodium hydroxide and zinc nitrate, zinc hydroxide forms as an insoluble solid, while sodium nitrate remains in solution. The identification of the insoluble precipitate is not only important for laboratory practices but also for environmental and industrial purposes where precipitation reactions can be utilized to remove undesired ions from solutions. Recognizing the formation of insoluble compounds allows us to selectively isolate certain elements from mixtures, purify compounds, and analyze the composition of solutions from precipitation patterns.