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 do not 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. \((\mathbf{d})\) 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, HF, SiF₄, H₂O. (c) SO₂, H₂O, H₂SO₃. (d) PH₃. (e) HClO₄, Cd, Cd(ClO₄)₂. (f) VBr₃.

Step-by-step solution

Identify Chemical Substances in Description (a)

The description mentions zinc carbonate, zinc oxide, and carbon dioxide. We need to determine their chemical formulas: - Zinc carbonate is ZnCO₃. - Zinc oxide is ZnO. - Carbon dioxide is CO₂.

Identify Chemical Substances in Description (b)

The description mentions silicon dioxide, hydrofluoric acid, silicon tetrafluoride, and water. Their formulas are: - Silicon dioxide is SiO₂. - Hydrofluoric acid is HF. - Silicon tetrafluoride is SiF₄. - Water is H₂O.

Identify Chemical Substances in Description (c)

The substances mentioned are sulfur dioxide, water, and sulfurous acid. Their formulas are: - Sulfur dioxide is SO₂. - Water is H₂O. - Sulfurous acid is H₂SO₃.

Identify Chemical Substance in Description (d)

The description mentions phosphorus trihydride, also known as phosphine, which is a common name for the chemical formula PH₃.

Identify Chemical Substances in Description (e)

The substances mentioned are perchloric acid, cadmium, and cadmium(II) perchlorate. Their formulas are: - Perchloric acid is HClO₄. - Cadmium is Cd. - Cadmium(II) perchlorate is Cd(ClO₄)₂.

Identify Chemical Substance in Description (f)

The description mentions vanadium(III) bromide, whose chemical formula is VBr₃.

Key concepts

Zinc Carbonate

Understanding zinc carbonate begins with recognizing it as a chemical compound composed of zinc, carbon, and oxygen. The chemical formula for this compound is \( \text{ZnCO}_3 \). Zinc carbonate is known for its use in a variety of applications, including as a precursor to other zinc compounds. It naturally occurs in the mineral smithsonite and bears a white to off-white appearance.

• **Decomposition of Zinc Carbonate**: When heated, zinc carbonate decomposes to form zinc oxide (\( \text{ZnO} \)) and carbon dioxide (\( \text{CO}_2 \)). This particular reaction is notable because it connects to zinc’s role in reactions requiring heat. The equation for this decomposition is: \[ \text{ZnCO}_3 (s) \rightarrow \text{ZnO} (s) + \text{CO}_2 (g) \]
• **Applications**: Zinc carbonate is utilized in medicinal ointments and as a mild astringent to relieve skin irritations. Furthermore, it serves roles in cosmetics and as an ingredient in some rubber products.

Silicon Dioxide

Silicon dioxide, also known as silica, is an abundant compound present in the Earth's crust and is composed of silicon and oxygen. The formula for silicon dioxide is \( \text{SiO}_2 \). Silicon dioxide is found naturally in various forms, from quartz crystals to sand.

• **Chemical Reactions**: When treated with hydrofluoric acid, \( \text{SiO}_2 \) reacts to form silicon tetrafluoride (\( \text{SiF}_4 \)) and water (\( \text{H}_2\text{O} \)). The balanced chemical equation for this reaction is: \[ \text{SiO}_2 (s) + 4\text{HF} (aq) \rightarrow \text{SiF}_4 (g) + 2\text{H}_2\text{O} (l) \]
• **Uses and Occurrence**: Silicon dioxide is central to the manufacturing of glass and ceramics. It is also used in the food industry as a flow agent in powdered foods. In nature, it is vital to many geological processes.

Sulfurous Acid

Sulfurous acid is a chemical compound with the formula \( \text{H}_2\text{SO}_3 \). It forms when sulfur dioxide (\( \text{SO}_2 \)) dissolves in water (\( \text{H}_2\text{O} \)). Although rarely found in a pure state, sulfurous acid is significant in aqueous solutions.

• **Formation**: The reaction involved in the creation of sulfurous acid is as follows: \[ \text{SO}_2 (g) + \text{H}_2\text{O} (l) \rightarrow \text{H}_2\text{SO}_3 (aq) \]
• **Importance**: This compound is noteworthy in environmental chemistry, especially concerning acid rain formation. It is often examined in atmospheric chemistry studies.
• **Applications**: In industry, sulfurous acid is used as a reducing agent and a disinfectant. It also serves in the mechanical pulping processes of paper manufacturing.

Perchloric Acid

Perchloric acid is a powerful oxidizing agent with the chemical formula \( \text{HClO}_4 \). It is a highly corrosive and colorless liquid and is one of the strongest acids available. Perchloric acid is used primarily in analytical chemistry.

• **Chemical Reactions**: An example of its reactivity is the reaction with cadmium to form cadmium(II) perchlorate (\( \text{Cd(ClO}_4)_2 \)). The balanced chemical reaction is: \[ \text{2HClO}_4 (aq) + \text{Cd} (s) \rightarrow \text{Cd(ClO}_4)_2 (aq) + \text{H}_2 (g) \]
• **Uses**: It is a key component in the preparation of perchlorate salts and is used in etching processes and for preparing rocket fuel.
• **Safety**: Special handling is required because it is both corrosive and explosive under certain conditions, necessitating strict safety measures.

Vanadium Bromide

Vanadium(III) bromide is a chemical compound with the formula \( \text{VBr}_3 \). It is an inorganic compound composed of vanadium and bromine.

• **Appearance and Properties**: As a colored solid, vanadium bromide is typically dark brown to black in appearance. It is not soluble in water but may dissolve in non-aqueous solvents.
• **Industrial Applications**: Vanadium bromide is used in research settings for vanadium catalysis and as a precursor to other vanadium compounds. It has a more limited application in industrial processes compared to more common vanadium compounds.
• **Reactivity**: The compound participates in various chemical reactions that involve its role as a catalyst, particularly in organic reactions where bromine is added across double bonds.