Question

Without per forming detailed calculations, indicate why you would expect each of the following reactions to occur to a significant extent as written. Use data from Appendix D as necessary. (a) \(\mathrm{BaCO}_{3}(\mathrm{s})+2 \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(\mathrm{aq}) \longrightarrow \mathrm{Ba}^{2+}(\mathrm{aq})+\) \(2 \mathrm{CH}_{3} \mathrm{CO}_{2}^{-}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{I})+\mathrm{CO}_{2}(\mathrm{g})\) (b) \(\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s})+2 \mathrm{NH}_{4}+(\mathrm{aq}) \longrightarrow\) \(\mathrm{Ca}^{2+}(\mathrm{aq})+2 \mathrm{NH}_{3}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(1)\) (c) \(\operatorname{BaF}_{2}(\mathrm{s})+2 \mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq}) \longrightarrow\) \(\mathrm{Ba}^{2+}(\mathrm{aq})+2 \mathrm{HF}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})\)

Short answer

The reactions (a), (b), and (c) occur to a significant extent because they all result in the dissolution of solutes into water and formation of strong acids or bases.

Step-by-step solution

Analyzing Reaction (a)

BaCO3 reacting with CH3CO2H allows the BaCO3 (a solid) to dissolve and form Ba2+(aq), CH3CO2-(aq), H2O(l), and CO2(g). The reaction of the strong acid (CH3CO2H) will help dissolve the solid BaCO3, hence the reaction will occur as written to a significant extent.

Analyzing Reaction (b)

Ca(OH)2 reacting with NH4+ would result in dissolving of Ca(OH)2 (a solid) and form aqueous solutions of Ca2+ and NH3 along with H2O. The ions from NH4+ will react with OH- ions from Ca(OH)2. Since both reactants are strong bases they will react significantly to give the products.

Analyzing Reaction (c)

BaF2 reacts with H3O+ to form Ba2+(aq), HF(aq), and H2O(l). F- ions from the recently dissociated BaF2 would bond with H+ ions from H3O+ to form HF(aq), while at the same time increasing the concentration of water. This implies that reaction will proceed in the direction that results in an aqueous solution.

Key concepts

Equilibrium Reactions

Understanding equilibrium reactions is crucial in predicting whether a chemical reaction will proceed as written. These reactions can reach a state where the rate of the forward reaction equals the rate of the reverse reaction, resulting in no net change in the concentration of products and reactants. This state is called dynamic equilibrium.

Many factors influence equilibrium, such as concentration, temperature, and pressure. Le Chatelier's Principle states that if an external change is applied to a system at equilibrium, the system will adjust itself to counteract that change and restore a new equilibrium.

In the context of Reaction (a), BaCO3 reacts with CH3CO2H, a strong acid. Here, Le Chatelier's Principle can be applied because the production of gas (CO2) and water (H2O) will shift the equilibrium to the right, favoring the formation of products.

For Reaction (b), the presence of NH4+ prompts the reaction with OH- ions from Ca(OH)2, shifting equilibrium to produce more NH3 and H2O. Reaction (c) sees BaF2 reacting with H3O+ to produce Ba2+, HF(aq), and additional water. In this case, removal of F- ions by forming HF drives the equilibrium towards the product side.

Acid-Base Reactions

Acid-base reactions are characterized by the transfer of protons (H+) from acids to bases. An acid is a substance that donates protons, whereas a base is a substance that accepts protons.

In Reaction (a), the CH3CO2H (acetic acid) donates H+ ions that react with carbonate, BaCO3, a base, resulting in the formation of CO2 gas and water. This is an example of an acid reacting with a carbonate base, which typically results in the production of CO2 and H2O.

Reaction (b) is another acid-base reaction where Ca(OH)2, a strong base, reacts with NH4+ which functions as a weak acid due to its ability to donate H+ ions. The reaction produces Ca2+ and NH3, another weak base, along with water. These acid-base interactions often result in soluble products and are usually favored to occur to a significant extent when strong acids or bases are involved.

Solubility Principles

Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. The solubility of compounds is influenced by factors like temperature, the polarity of the solvent and solute, and pressure.

For ionic compounds like BaCO3, Ca(OH)2, and BaF2 mentioned in Reactions (a), (b), and (c) respectively, their solubilities in water are essential in predicting the extent of the reactions. In terms of solubility principles, an acid reacting with a base generally increases the solubility of the base, especially if a gas is produced or if the reaction results in the formation of water.

In Reaction (a), acetic acid increases the solubility of BaCO3 by producing soluble ions (Ba2+ and CH3CO2-) along with CO2 and H2O, which encourages the reaction to proceed. Similarly, solubility principles suggest that the production of NH3 and water in Reaction (b) would favor the dissolution of Ca(OH)2. Lastly, in Reaction (c), protons from H3O+ react with BaF2, increasing its solubility by forming soluble Ba2+ ions and HF in water.