Question

For each of the following slightly soluble salts, write the net ionic equation, if any, for reaction with acid: (a) MnS, (b) \(\mathrm{PbF}_{2},\) (c) \(\mathrm{AuCl}_{3}\) (e) CuBr. (d) \(\mathrm{Hg}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\)

Short answer

Net ionic equations for the reaction of slightly soluble salts with acid are as follows: a) \(MnS (s) + 2H^{+} (aq) \rightarrow Mn^{2+} (aq) + H_{2}S(g)\) b) \(PbF_{2} (s) + 2H^{+} (aq) \rightarrow Pb^{2+} (aq) + 2HF (g)\) c) \(AuCl_{3} (s) + 3H^{+} (aq) \rightarrow Au^{3+} (aq) + 3HCl (g)\) d) \(Hg_{2}C_{2}O_{4} (s) + 2H^{+} (aq) \rightarrow Hg^{2+} (aq) + 2H_{2}C_{2}O_{4} (aq)\) e) \(CuBr (s) + H^{+} (aq) \rightarrow Cu^{2+} (aq) + HBr (g)\)

Step-by-step solution

Write the balanced molecular equation

MnS (s) + 2H+ (aq) → Mn2+ (aq) + H2S(g)

Break the compounds into their respective ions

MnS (s) → Mn2+ (aq) + S2- (aq) 2H+ (aq) → 2H+ (aq) Mn2+ (aq) + H2S(g) → Mn2+ (aq) + H2S(g)

Write the net ionic equation

MnS (s) + 2H+ (aq) → Mn2+ (aq) + H2S(g) #b) \(\mathrm{PbF}_{2}\) with Acid#

Write the balanced molecular equation

\(\mathrm{PbF}_{2}\) (s) + 2H+ (aq) → Pb2+ (aq) + 2HF (g)

Break the compounds into their respective ions

\(\mathrm{PbF}_{2}\) (s) → Pb2+ (aq) + 2F- (aq) 2H+ (aq) → 2H+ (aq) Pb2+ (aq) + 2HF (g) → Pb2+ (aq) + 2HF (g)

Write the net ionic equation

\(\mathrm{PbF}_{2}\) (s) + 2H+ (aq) → Pb2+ (aq) + 2HF (g) #c) \(\mathrm{AuCl}_{3}\) with Acid#

Write the balanced molecular equation

\(\mathrm{AuCl}_{3}\) (s) + 3H+ (aq) → Au3+ (aq) + 3HCl (g)

Break the compounds into their respective ions

\(\mathrm{AuCl}_{3}\) (s) → Au3+ (aq) + 3Cl- (aq) 3H+ (aq) → 3H+ (aq) Au3+ (aq) + 3HCl (g) → Au3+ (aq) + 3HCl (g)

Write the net ionic equation

\(\mathrm{AuCl}_{3}\) (s) + 3H+ (aq) → Au3+ (aq) + 3HCl (g) #d) \(\mathrm{Hg}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) with Acid#

Write the balanced molecular equation

\(\mathrm{Hg}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) (s) + 2H+ (aq) → Hg2+ (aq) + 2H2C2O4 (aq)

Break the compounds into their respective ions

\(\mathrm{Hg}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) (s) → Hg2+ (aq) + 2C2O42- (aq) 2H+ (aq) → 2H+ (aq) Hg2+ (aq) + 2H2C2O4 (aq) → Hg2+ (aq) + 2H2C2O4 (aq)

Write the net ionic equation

\(\mathrm{Hg}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) (s) + 2H+ (aq) → Hg2+ (aq) + 2H2C2O4 (aq) #e) CuBr with Acid#

Write the balanced molecular equation

CuBr (s) + H+ (aq) → Cu2+ (aq) + HBr (g)

Break the compounds into their respective ions

CuBr (s) → Cu2+ (aq) + Br- (aq) H+ (aq) → H+ (aq) Cu2+ (aq) + HBr (g) → Cu2+ (aq) + HBr (g)

Write the net ionic equation

CuBr (s) + H+ (aq) → Cu2+ (aq) + HBr (g)

Key concepts

Slightly Soluble Salts

Slightly soluble salts are ionic compounds that don't completely dissolve in water. These salts form a solid precipitate instead of fully dissociating into their respective ions in solution. Imagine them as a sprinkle of sugar on top of your lemonade - they don't fully mix. Examples include manganese sulfide (MnS) and lead fluoride (\( \mathrm{PbF}_{2} \)).

Understanding slightly soluble salts is crucial because they often participate in reactions where one or more components are insoluble. When these salts interact with acids, a chemical reaction takes place, often leading to their dissolution. This happens because the acid provides hydrogen ions (H⁺), which can react with the anion of the slightly soluble salt to form a soluble product.

In conclusion, knowing which salts are slightly soluble can help predict whether a reaction with an acid will lead to a product that dissolves in water, forming a net ionic equation.

Reactions with Acid

When slightly soluble salts react with acids, the aim is often to dissolve the salt by forming simpler, soluble products. Acids, like \( \mathrm{HCl} \), provide H⁺ ions to react with the anions of the salt. In converting the insoluble compound into a form that dissolves, gases or water-soluble products are typically produced.

Some reactions with acid result in the release of a gas. For example, when MnS reacts with an acid, it produces H₂S gas. Other reactions lead to the formation of water-soluble compounds like HF from \( \mathrm{PbF}_{2} \), which helps dissolve the original salt.

Understanding these reactions involves more than just predicting whether a salt will dissolve in an acid. It's about realizing the products you get, like gases or soluble ionic compounds, and knowing how they impact the overall reaction.

Chemical Equations

Chemical equations are the language chemists use to represent reactions. They show the reactants transforming into products through a balanced expression of chemical symbols. For slightly soluble salts reacting with acids, we start with a molecular equation that represents the overall reaction.

A balanced molecular equation must have the same number of each type of atom on both sides of the equation. After writing it, break down each compound into ions to view the ionic reaction, including only ions that participate directly in the chemical change, excluding spectator ions (which do not change during the reaction).

Finally, the net ionic equation is written to show only the ions and molecules directly involved in the formation of the products. This simplifies the analysis of the reaction and helps focus on the essential transformations.

Ionic Compounds

Ionic compounds are formed by the electrostatic attraction between oppositely charged ions. Typically, they consist of a metal cation and a non-metal anion. For example, in MnS, manganese (Mn²⁺) is paired with sulfide (S^2-).

These compounds’ solubility varies; while many ionic compounds dissolve readily in water, some like \( \mathrm{CuBr} \), are only slightly soluble. This limited solubility can predict how a compound will behave in solution or when mixed with acids.

In an ionic reaction, such as those involved in this exercise, the focus is on the ions in solution. By simplifying a chemical equation into its ionic form, we can clearly see the movement of ions from reactants to products, better understanding how ionic compounds interact within aqueous environments.