Question

The compound formed when gypsum is dissolved in aqueous ammonium sulphate solution is (a) \(\mathrm{CaSO}_{4} \cdot \mathrm{NH}_{3} \mathrm{Cl} . \mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{CaSO}_{4} \cdot\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} \cdot \mathrm{H}_{2} \mathrm{O}\) (c) \(\mathrm{CaCl}_{2} . \mathrm{NH}_{4} \mathrm{Cl} .2 \mathrm{H}_{2} \mathrm{O}\) (d) \(\mathrm{CaCl}_{2} \cdot\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} \cdot \mathrm{H}_{2} \mathrm{O}\)

Short answer

The compound formed is (b) \(\mathrm{CaSO}_{4} \cdot\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}\cdot \mathrm{H}_{2} \mathrm{O}\).

Step-by-step solution

Understand the reactants

Gypsum is primarily composed of calcium sulfate dihydrate, with the chemical formula \(\text{CaSO}_4 \cdot 2\text{H}_2\text{O}\). In this problem, it is being dissolved in an aqueous solution of ammonium sulfate, \(\text{(NH}_4\text{)}_2\text{SO}_4\). The interaction between these compounds will determine the product formed.

Predict the chemical reaction

When gypsum \((\text{CaSO}_4 \cdot 2\text{H}_2\text{O})\) is dissolved in ammonium sulfate \((\text{(NH}_4\text{)}_2\text{SO}_4)\) solution, double displacement reactions can occur typically involving cation exchange. The possible compound formation can be \(\text{CaSO}_4 \cdot (\text{NH}_4\text{)}_2\text{SO}_4 \cdot \text{H}_2\text{O}\).

Identify the most feasible product

Considering typical double displacement reactions, the formation of \(\text{CaSO}_4 \cdot (\text{NH}_4\text{)}_2\text{SO}_4 \cdot \text{H}_2\text{O}\) is feasible as it incorporates components from both gypsum and ammonium sulfate, without forming unexpected bonds like \(\text{Cl}\) that are not present in the original reactants.

Match the product with given options

Reviewing the options, option (b) \(\text{CaSO}_4 \cdot (\text{NH}_4\text{)}_2\text{SO}_4 \cdot \text{H}_2\text{O}\) matches our predicted product, making it the correct choice.

Key concepts

Gypsum Chemistry

Gypsum is a soft sulfate mineral composed primarily of calcium sulfate dihydrate, with the chemical formula \( \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \). It is a widely used raw material in various applications such as construction, agriculture, and even art. When we speak about gypsum chemistry, it is important to consider this mineral's solubility and its behavior in different solutions.

In water, gypsum is partially soluble and carries this attribute into reactions with other compounds. The hydration structure of gypsum helps it retain moisture, making it distinctive in comparison to other anhydrous salts. When gypsum comes into contact with ammonium sulfate in an aqueous solution, it engages in a chemical reaction that leads to the formation of a new compound.

The dynamics of gypsum in chemical reactions revolve around its ability to participate in double displacement reactions. During such reactions, the components swap partners, leading to the formation of products that incorporate sulfate and calcium ions from gypsum and other ions from the reactant. This adaptability highlights gypsum's role in industrial and chemical processes.

Ammonium Sulfate Reactions

Ammonium sulfate, represented by \( (\text{NH}_4)_2\text{SO}_4 \), is a commonly used inorganic salt with applications in fertilizers and industrial chemistry. Its most crucial aspect in reactions is its ability to dissociate into ammonium \((\text{NH}_4^+)\) and sulfate \((\text{SO}_4^{2-})\) ions in solution.

This dissociation facilitates ammonium sulfate's participation in double displacement reactions. In these processes, ammonium sulfate swaps ions with other compounds, as seen when it reacts with gypsum. The critical skill when working with these reactions is understanding how the ions rearrange to form stable new products.

Typically, the products that form are those that combine the ions from the original reactants into an energetically favorable arrangement. For instance, when gypsum and ammonium sulfate interact, the reaction is governed largely by the tendency of the sulfate ions to find suitable cations to bond with, while forming stable components like \( \text{CaSO}_4 \cdot (\text{NH}_4)_2\text{SO}_4 \cdot \text{H}_2\text{O} \). Ammonium sulfate's reactivity and swapping abilities in solutions make it valuable in creating novel compounds.

Predicting Chemical Reactions

Predicting chemical reactions involves understanding the nature of the reactants and the possible products they can form. For double displacement reactions, also known as metathesis reactions, it is often a matter of exchanging ions between two compounds.

Take the example of gypsum \((\text{CaSO}_4 \cdot 2\text{H}_2\text{O})\) and ammonium sulfate \((\text{NH}_4)_2\text{SO}_4\). The art of prediction lies in recognizing the mobile ions: \(\text{Ca}^{2+}\), \(\text{NH}_4^+\), and \(\text{SO}_4^{2-}\). One can anticipate that these ions will swap partners to form a new, energetically favorable compound.

Factors influencing the products include the solubility of the resulting compounds and the stability of the formed bonds. Energetically viable configurations are preferred, meaning options with the least potential energy are often formed. In handling problems like predicting the product of gypsum dissolved in aqueous ammonium sulfate, being grounded in these principles is key to accurately foreseeing the result, which in this case is \(\text{CaSO}_4 \cdot (\text{NH}_4)_2\text{SO}_4 \cdot \text{H}_2\text{O} \).

Mastering these predictions can vastly improve problem-solving skills in chemistry, making complex reactions more approachable and understandable.