Problem 79 - Chemistry: The Central Science in SI Units, Global Edition

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. (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.

Step-by-Step Solution

Answer

The chemical formulas for each reaction are: (a) ZnCO3 → ZnO + CO2 (b) SiO2 + HF → SiF4 + H2O (c) SO2 + H2O → H2SO3 (d) PH3 (e) HClO4 + Cd → Cd(ClO4)2 (f) VBr3

Step 1: 1. Zinc carbonate to zinc oxide and carbon dioxide

In this reaction, zinc carbonate is being heated to form zinc oxide and carbon dioxide. The chemical formula for zinc carbonate is ZnCO3, for zinc oxide is ZnO, and for carbon dioxide is CO2.

Step 2: 2. Silicon dioxide with hydrofluoric acid

In this reaction, silicon dioxide reacts with hydrofluoric acid to form silicon tetrafluoride and water. The chemical formula for silicon dioxide is SiO2, for hydrofluoric acid is HF, for silicon tetrafluoride is SiF4, and for water is H2O.

Step 3: 3. Sulfur dioxide with water

In this reaction, sulfur dioxide reacts with water to form sulfurous acid. The chemical formula for sulfur dioxide is SO2, for water is H2O, and for sulfurous acid is H2SO3.

Step 4: 4. Phosphorus trihydride (phosphine)

Phosphorus trihydride, also known as phosphine, is a toxic gas. The chemical formula for phosphorus trihydride is PH3.

Step 5: 5. Perchloric acid with cadmium

In this reaction, perchloric acid reacts with cadmium to form cadmium(II) perchlorate. The chemical formula for perchloric acid is HClO4, for cadmium is Cd, and for cadmium(II) perchlorate is Cd(ClO4)2.

Step 6: 6. Vanadium(III) bromide

Vanadium(III) bromide is a colored solid. The chemical formula for vanadium(III) bromide is VBr3.

Key Concepts

Zinc Carbonate

Zinc carbonate is a chemical compound with the formula \( \text{ZnCO}_3 \). It is composed of zinc, carbon, and oxygen.
When zinc carbonate is heated, it decomposes to form zinc oxide \( \text{ZnO} \) and carbon dioxide \( \text{CO}_2 \).

• Zinc oxide is a white powder used in various applications, including skin protection and as a pigment.
• Carbon dioxide is a colorless gas commonly found in the atmosphere.

The process or reaction of zinc carbonate turning into zinc oxide and carbon dioxide under heat is an example of thermal decomposition, which is common among carbonates.

Silicon Dioxide

Silicon dioxide, known widely as silica, has the chemical formula \( \text{SiO}_2 \). It is commonly found in nature as quartz.

• This compound reacts with hydrofluoric acid \( \text{HF} \) to produce silicon tetrafluoride \( \text{SiF}_4 \) and water \( \text{H}_2\text{O} \).
• Hydrofluoric acid is highly corrosive and is used to etch glass and other materials.

The reaction of silicon dioxide with hydrofluoric acid is significant in industrial chemistry and illustrates how reactive silica can be under certain conditions.

Phosphorus Trihydride

Phosphorus trihydride is an alternative name for phosphine, a chemical with the formula \( \text{PH}_3 \).
This compound is a toxic and flammable gas with a strong fish-like odor.

• Due to its toxicity, phosphine is used in pest control and can pose health risks if inhaled or handled improperly.
• Phosphine is also an important compound in organophosphorus chemistry.

Understanding the properties of phosphorus trihydride is crucial for safely handling it and using it effectively for industrial purposes.

Sulfur Dioxide

Sulfur dioxide \( \text{SO}_2 \) is a colorless gas with a pungent smell often associated with burning sulfur.
It interacts with water to produce sulfurous acid \( \text{H}_2\text{SO}_3 \), which is part of many chemical processes.

• Sulfur dioxide is used as a preservative due to its antimicrobial properties.
• It is also a significant environmental pollutant, contributing to acid rain.

The reaction of sulfur dioxide with water is an essential aspect of atmospheric chemistry, particularly in understanding the effects of pollution.

Perchloric Acid

Perchloric acid \( \text{HClO}_4 \) is a strong acid known for its oxidizing properties.
It reacts with cadmium \( \text{Cd} \) to form cadmium(II) perchlorate \( \text{Cd(ClO}_4)_2 \), which is often used in laboratory settings.

• Perchloric acid must be handled with care as it can be highly reactive and potentially explosive under certain conditions.
• Its applications include the preparation of perchlorate salts and use in etching and cleaning.

The interaction of perchloric acid with metals like cadmium is a showcase of its strong acid properties and versatility in chemistry.

Vanadium(III) Bromide

Vanadium(III) bromide has the chemical formula \( \text{VBr}_3 \) and is a solid compound known for its distinctive color.

• This compound consists of vanadium, a transition metal, and bromine, a halogen.
• Vanadium(III) bromide is utilized in various chemical reactions, particularly in organic synthesis as a catalyst or in the reduction of certain compounds.

Its properties make it a valuable reagent in laboratory settings, where understanding its chemical behavior is crucial for effective use.