Problem 70 - General Chemistry

Question

Identify each of the following compounds. a. An acidic compound that also has properties of an aldehyde; its molecular formula is \(\mathrm{CH}_{2} \mathrm{O}_{2}\). b. A compound used as a preservative for biological specimens and as a raw material for plastics. c. A saturated hydrocarbon boiling at \(0^{\circ} \mathrm{C}\) that is liquefied and sold in cylinders as a fuel. d. A saturated hydrocarbon that is the main constituent of natural gas.

Step-by-Step Solution

Answer

a. Formic acid; b. Formaldehyde; c. Propane; d. Methane.

Step 1: Identify the Acidic Aldehyde

Given the molecular formula \( \text{CH}_2\text{O}_2 \), we suspect the compound might be formic acid, which is an aldehyde (with one aldehydic carbonyl group) and also has acidic properties (due to the carboxyl group).

Step 2: Identify the Preservative Compound

Formaldehyde, also known as methanal, is commonly used as a preservative for biological specimens. It is also a key raw material in the production of plastics, such as phenolic resins.

Step 3: Identify the Liquefied Fuel Hydrocarbon

The compound that is a saturated hydrocarbon, boils at \(0^{\circ} \text{C}\), and is commonly sold in cylinders as a fuel is propane \( \text{C}_3\text{H}_8 \).

Step 4: Identify the Main Constituent of Natural Gas

Methane \( \text{CH}_4 \) is a saturated hydrocarbon that is the main constituent of natural gas, known for being a major source of energy.

Key Concepts

Acidic Compounds

Acidic compounds are a fascinating group in chemistry that have the ability to donate protons (H+) to other substances, a property known as acidity. In the context of the exercise, formic acid is an example of an acidic compound with a unique twist. Formic acid not only has acidic properties due to its carboxyl group but also contains an aldehyde group. This combination allows it to function as both an acid and an aldehyde, making it quite versatile. Formic acid, with the formula \( \text{CH}_2\text{O}_2 \), is often used in various chemical reactions and industrial processes due to these dual properties.

Aldehydes

Aldehydes are organic compounds characterized by the presence of a carbonyl group (C=O) bonded to a hydrogen atom and an R group, which can be a carbon chain or ring. This structure is represented as \( \text{R}-\text{CHO} \). Aldehydes are significant in both industrial roles and biological processes. An example from our exercise is formaldehyde, known scientifically as methanal. It is a simple aldehyde with the formula \( \text{CH}_2\text{O} \), and is renowned for its use in preserving biological specimens. Additionally, formaldehyde is a precursor to more complex molecules, such as plastics, which are essential in modern life.

Saturated Hydrocarbons

Saturated hydrocarbons, or alkanes, are simple organic compounds consisting entirely of single bonds between carbon atoms, with the maximum number of hydrogen atoms attached. This means they have no double or triple bonds, resulting in a structure that is 'saturated' with hydrogen. A classic example is propane \( \text{C}_3\text{H}_8 \), which is often used as a fuel. Propane is a colorless gas at room temperature but can be liquefied for practical storage and transportation. Its low boiling point of \(0^{\circ} \text{C} \) makes it suitable for various heating applications, especially in areas without natural gas pipelines.

Natural Gas Constituent

Natural gas is primarily composed of methane, a simple alkane with the chemical formula \( \text{CH}_4 \). As the main constituent of natural gas, methane plays a crucial role in the global energy supply. It is highly efficient as a fuel due to its high energy content and cleaner combustion compared to other fossil fuels. Methane's simple structure with one carbon atom and four hydrogen atoms makes it highly combustible. Its abundance and efficiency as a fuel source make it a popular choice for both residential heating and electricity generation, significantly impacting the energy landscape worldwide.