Problem 100 - General Chemistry: Principles and Modern Applications

Question

A good example of a homogeneous mixture is (a) a cola drink in a tightly capped bottle (b) distilled water leaving a distillation apparatus (c) oxygen gas in a cylinder used in welding (d) the material produced in a kitchen blender

Step-by-Step Solution

Answer

The right answer is (a) a cola drink in a tightly capped bottle.

Step 1: Understanding the choices

Analyze all the options given: (a) a cola drink in a tightly capped bottle signifies a homogeneous mixture because, once bottled and shaken, the cola drink has a uniform composition throughout. (b) Distilled water leaving a distillation apparatus implies a pure substance, not a mixture. (c) Oxygen gas in a welding cylinder denotes a pure substance rather than a mixture. (d) The material produced in a kitchen blender depends on what material is used, though generally this could be a heterogeneous mixture because the material can be separated.

Step 2: Choosing the correct answer

Choose the option that best fits the definition of a homogeneous mixture. In this case, the most obvious choice is (a) a cola drink in a tightly capped bottle, as it displays uniformity throughout its composition.

Key Concepts

pure substances

Pure substances are materials composed of only one type of particle. This means they are composed of a single element or a single compound. There are no other substances mixed in with them. Pure substances have a uniform and definite composition throughout.

Some key features of pure substances include:

• Definite Melting and Boiling Points: Pure substances have precise melting and boiling points, unlike mixtures which may have a range of temperatures for these changes.
• Constant Composition: Regardless of the sample size, the composition of a pure substance is always the same.
• Homogeneity: At the molecular level, pure substances are homogeneous. However, in some discussions, especially in schoolwork, homogeneous often refers to mixtures that appear uniform in everyday contexts.

Examples include pure water, pure oxygen, and gold.

distilled water

Distilled water is a common example of a pure substance. It is water that has been purified through the process of distillation, which involves boiling the water and then condensing the steam back into a liquid. This process removes impurities and minerals from the water, leaving behind pure H₂O.

Characteristics of distilled water:

• Purity: Distilled water is free from dissolved salts, minerals, and organic materials.
• Neutral pH: It is neutral with a pH of around 7, making it neither acidic nor basic.
• Uses: It is often used in laboratories and medical settings where pure water is essential. Additionally, it is used in car batteries and in devices where mineral deposits could cause damage.

Distilled water, as a pure substance, contrasts with mixtures which contain multiple substances blended together.

oxygen gas

Oxygen gas is another excellent example of a pure substance. As a crucial element of the periodic table, it is denoted by the symbol O and is critical for various life-sustaining processes.

Here are essential details about oxygen gas:

• Composition: Oxygen gas consists of molecules made up of two oxygen atoms, represented as O₂.
• Properties: It is a colorless, odorless gas at room temperature, and it supports combustion, hence its use in welding and other industrial applications.
• Significance in Life: Oxygen is vital for cellular respiration in animals and plants, where it helps convert nutrients into energy.

As a pure substance, it differs from mixtures, which involve the physical combination of two or more different substances.

blender mixtures

Blender mixtures refer to the various ingredients that are combined and processed in a blender. This process typically results in a heterogeneous mixture. A blender can mix together fruits, vegetables, and other ingredients, but the outcome often remains a combination of different textures and compositions.

Consider the following characteristics:

• Variety: Depending on the ingredients used, the mixture can vary greatly both in consistency and taste.
• Lack of Uniformity: Unlike homogeneous mixtures, the contents of a blender might not be evenly distributed throughout. The mixture can contain different parts that are still distinguishable.
• Common Examples: Smoothies and soups are typical products of blender mixtures, showcasing varied ingredients blended together.

Blender mixtures highlight the distinction between homogenized mixtures and those which remain diverse in composition and texture.