Question

Write the chemical formula for each substance mentioned in the following word descriptions (use the front inside cover to find the symbols for the elements you don't know). (a) Zinc carbonate can be heated to form zinc oxide and carbon dioxide. (b) On treatment with hydrofluoric acid, silicon dioxide forms silicon tetrafluoride and water. (c) Sulfur dioxide reacts with water to form sulfurous acid. (d) The substance phosphorus trihydride, commonly called phosphine, is a toxic gas. (e) Perchloric acid reacts with cadmium to form cadmium(II) perchlorate. (f) Vanadium(III) bromide is a colored solid.

Short answer

(a) ZnCO3 → ZnO + CO2 (b) SiO2 + 4HF → SiF4 + 2H2O (c) SO2 + H2O → H2SO3 (d) PH3 (e) HClO4 + Cd → Cd(ClO4)2 (f) VBr3

Step-by-step solution

(a) Zinc carbonate forming zinc oxide and carbon dioxide

To write the chemical formula for zinc carbonate, we need to find the symbols for zinc and carbonate ions. Zinc (Zn) forms a 2+ ion and carbonate (CO3) forms a 2- ion. Therefore, the formula for zinc carbonate is ZnCO3. When heated, zinc carbonate decomposes into zinc oxide (ZnO) and carbon dioxide (CO2). So the overall reaction is: ZnCO3 (s) → ZnO (s) + CO2 (g)

(b) Silicon dioxide and hydrofluoric acid forming silicon tetrafluoride and water

The chemical formula for silicon dioxide is SiO2, and for hydrofluoric acid, it is HF. When silicon dioxide reacts with hydrofluoric acid, it forms silicon tetrafluoride (SiF4) and water (H2O). The balanced chemical equation for this reaction is: SiO2 (s) + 4HF (aq) → SiF4 (g) + 2H2O (l)

(c) Sulfur dioxide and water forming sulfurous acid

Sulfur dioxide (SO2) reacts with water (H2O) to form sulfurous acid (H2SO3). The balanced chemical equation for this reaction looks like this: SO2 (g) + H2O (l) → H2SO3 (aq)

(d) Phosphorus trihydride

Phosphorus trihydride is more commonly referred to as phosphine. The chemical formula for phosphorus trihydride (phosphine) is PH3.

(e) Perchloric acid and cadmium forming cadmium(II) perchlorate

Perchloric acid has the formula HClO4, and cadmium (Cd) forms a 2+ ion. When cadmium reacts with perchloric acid, it forms cadmium(II) perchlorate, which has the formula Cd(ClO4)2, since perchlorate has a 1- charge.

(f) Vanadium(III) bromide

Vanadium(III) means that vanadium (V) has a 3+ charge. Bromide (Br) has a 1- charge. Therefore, the chemical formula for vanadium(III) bromide is VBr3 since it requires three bromide ions to balance the 3+ charge of vanadium.

Key concepts

Zinc Carbonate

Zinc carbonate, with the chemical formula \( \text{ZnCO}_3 \), is an interesting compound that combines zinc and carbonate ions. Zinc ion is represented by \( \text{Zn}^{2+} \), and the carbonate ion is represented by \( \text{CO}_3^{2-} \). These charges cancel each other out, resulting in the neutral compound ZnCO3.

When subjected to heat, zinc carbonate undergoes decomposition. During this process, it breaks down to form zinc oxide \( \text{ZnO} \) and carbon dioxide \( \text{CO}_2 \), which is a gas. The reaction can be simply represented as:

\[ \text{ZnCO}_3 (s) \rightarrow \text{ZnO} (s) + \text{CO}_2 (g) \]

This decomposition reaction is interesting not only from a chemistry standpoint but also in industrial processes, where zinc oxide is a useful product in the production of various materials.

Silicon Dioxide

Silicon dioxide, or \( \text{SiO}_2 \), is a common compound found in nature as quartz. It's also an essential component of sand, an important material in construction and technology. The compound consists of one silicon atom bound to two oxygen atoms.

When silicon dioxide interacts with hydrofluoric acid \( \text{HF} \), it undergoes a reaction to form silicon tetrafluoride \( \text{SiF}_4 \) and water \( \text{H}_2\text{O} \). The chemical reaction involved is:

\[ \text{SiO}_2 (s) + 4\text{HF} (aq) \rightarrow \text{SiF}_4 (g) + 2\text{H}_2\text{O} (l) \]

The reaction involving hydrofluoric acid is particularly significant due to the acid's ability to etch glass, showcasing its role in the decomposition of silica.

Sulfur Dioxide

Sulfur dioxide, with the formula \( \text{SO}_2 \), is a gaseous compound primarily known for its role as an air pollutant. However, when it reacts with water, it forms another interesting chemical known as sulfurous acid \( \text{H}_2\text{SO}_3 \).

The reaction can be summarized by the following equation:

\[ \text{SO}_2 (g) + \text{H}_2\text{O} (l) \rightarrow \text{H}_2\text{SO}_3 (aq) \]

Sulfurous acid is an unstable intermediate and is often a part of acid rain development. This reaction highlights the significance of sulfur dioxide in environmental chemistry and its impact on ecosystems.

Phosphine

Phosphine, also known as phosphorus trihydride, holds the chemical formula \( \text{PH}_3 \). It consists of one phosphorus atom covalently bonded to three hydrogen atoms.

This compound is a toxic and flammable gas that has a faint smell similar to garlic or rotten fish. Despite its toxicity, phosphine plays crucial roles in certain industrial applications, including its use as a pesticide and in the semiconductor industry.

Understanding phosphine's basic structure and properties is important for applications that require stringent safety measures.

Perchloric Acid

Perchloric acid \( \text{HClO}_4 \) is a highly reactive substance known for its strong acidic properties. The perchlorate ion \( \text{ClO}_4^- \) gives rise to various applications in industrial chemistry and explosives.

When perchloric acid reacts with metals, like cadmium \( \text{Cd} \), it forms metal perchlorates. An example of such a reaction is the formation of cadmium(II) perchlorate \( \text{Cd(ClO}_4)_2 \). This occurs due to the 2+ charge on cadmium balancing with two perchlorate ions, each having a 1- charge.

Perchloric acid reactions are vital in analytical chemistry and for the preparation of perchlorate salts, which have varied applications in different fields.

Vanadium(III) Bromide

Vanadium(III) bromide, \( \text{VBr}_3 \), is typically a colored solid. It results from the combination of vanadium in its +3 oxidation state and bromide ions, each carrying a 1- charge. Three bromide ions are required to balance one vanadium ion's charge.

This compound is involved in various chemical syntheses and had particular use in understanding transition metal chemistry. Vanadium compounds, including vanadium(III) bromide, illustrate the colorful world of chemistry due to their diverse oxidation states and resultant hues.

Through its distinct chemical structure, \( \text{VBr}_3 \) provides insight into how metal halides interact at the molecular level.