Problem 23 - Chemistry The Central Science

Question

Name the spectator ions in any reactions that may be involved when each of the following pairs of solutions are mixed. (a) \(\mathrm{Na}_{2} \mathrm{CO}_{3}(a q)\) and \(\mathrm{MgSO}_{4}(a q)\) (b) \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(a q)\) and \(\mathrm{Na}_{2} \mathrm{~S}(a q)\) (c) \(\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4}(a q)\) and \(\mathrm{CaCl}_{2}(a q)\)

Step-by-Step Solution

Answer

The spectator ions in the given reactions are: (a) Sodium ion (Na\(^+\)) and sulfate ion (SO\(_4^{2-}\)) (b) Sodium ion (Na\(^+\)) and nitrate ion (NO\(_3^-\)) (c) Ammonium ion (NH\(_4^+\)) and chloride ion (Cl\(^-\))

Step 1: (a) Write the balanced chemical equation for the reaction between Na2CO3 and MgSO4

The balanced chemical equation for the reaction between Na2CO3 and MgSO4 is: \(Na_2CO_3(aq)+MgSO_4(aq)\rightarrow MgCO_3(s)+2NaSO_4(aq)\)

Step 2: (a) Find the spectator ions for Na2CO3 and MgSO4 reaction

The spectator ions are the ones that do not participate in the reaction and remain in solution. In this case, the sodium ion (Na\(^+\)) and sulfate ion (SO\(_4^{2-}\)) are the spectator ions. They do not change during the reaction and remain in the solution.

Step 3: (b) Write the balanced chemical equation for the reaction between Pb(NO3)2 and Na2S

The balanced chemical equation for the reaction between Pb(NO3)2 and Na2S is: \(Pb(NO_3)_2(aq)+Na_2S(aq)\rightarrow PbS(s)+2NaNO_3(aq)\)

Step 4: (b) Find the spectator ions for Pb(NO3)2 and Na2S reaction

The spectator ions are the ones that do not participate in the reaction and remain in solution. In this case, the sodium ion (Na\(^+\)) and the nitrate ion (NO\(_3^-\)) are the spectator ions. They do not change during the reaction and remain in the solution.

Step 5: (c) Write the balanced chemical equation for the reaction between (NH4)3PO4 and CaCl2

The balanced chemical equation for the reaction between (NH4)3PO4 and CaCl2 is: \((NH_4)_3PO_4(aq)+CaCl_2(aq)\rightarrow Ca(PO_4)_2(s)+6NH_4Cl(aq)\)

Step 6: (c) Find the spectator ions for (NH4)3PO4 and CaCl2 reaction

The spectator ions are the ones that do not participate in the reaction and remain in solution. In this case, the ammonium ion (NH\(_4^+\)) and the chloride ion (Cl\(^-\)) are the spectator ions. They do not change during the reaction and remain in the solution.

Key Concepts

Balanced Chemical Equations

Understanding balanced chemical equations is fundamental to mastering chemistry. A balanced chemical equation represents a chemical reaction where the number of atoms for each element is equal on both the reactant and product sides. This conservation of mass is expressed by ensuring that for every type of atom present, the same number of that atom exists before and after the reaction.

For instance, in the reaction where sodium carbonate reacts with magnesium sulfate to form magnesium carbonate and sodium sulfate, the equation is written as: \[Na_2CO_3(aq) + MgSO_4(aq) \rightarrow MgCO_3(s) + 2NaSO_4(aq)\].In this equation, all atoms balance out on both sides, abiding by the Law of Conservation of Mass. Students should verify this by counting the atoms of each element. Understanding and being able to balance these equations is crucial, as it provides a clear picture of the exact quantities of reactants and products involved in chemical reactions.

Ion Exchange Reactions

Chemical reactions that involve ions moving from one compound to another are known as ion exchange reactions. These reactions often occur in solutions where dissolved compounds exchange ions to form new substances. This kind of reaction is typical in many inorganic chemical processes and can be easily demonstrated in the lab using aqueous solutions.

Diving into the provided problem, when a sodium carbonate (Na₂CO₃) solution is mixed with a magnesium sulfate (MgSO₄) solution, the two ionic compounds exchange ions. The Na⁺ ions pair up with SO₄^2- ions, and the Mg²⁺ ions pair with CO₃^2- ions, leading to the formation of a precipitate, magnesium carbonate (MgCO₃), and sodium sulfate remains in the solution. These reactions are easily predicted by understanding the solubility rules and recognizing which combinations of ions will produce an insoluble compound, resulting in a precipitate.

Solubility of Compounds

The solubility of compounds is a critical concept in chemistry which dictates whether a substance will dissolve in a particular solvent, such as water. Soluble substances can dissolve to form a homogeneous mixture, while insoluble substances will not dissolve and oftentimes form a precipitate in a reaction.

In the reactions you're studying, the solubility rules help predict the behavior of ionic compounds in aqueous solutions. For example, carbonates are generally insoluble unless they're paired with alkali metal ions like sodium or potassium, or the ammonium ion. That is why when we mix sodium carbonate with magnesium sulfate, magnesium carbonate precipitates out of the solution since it’s insoluble in water, leaving behind the soluble sodium sulfate. Students should familiarize themselves with basic solubility guidelines to better predict the outcomes of ion exchange reactions and identify spectator ions effectively.