Problem 7 - Campbell Biology Concepts & Connections

Question

A can of cola consists mostly of sugar dissolved in water, with some carbon dioxide gas that makes it fizzy and makes the pH less than \(7 .\) In chemical terms, you could say that cola is an aqueous solution where water is the _____, sugar is a _____, and carbon dioxide makes the solution _____. a. solvent ... solute ... basic b. solute ... solvent ... basic c. solvent ... solute ... acidic d. solute ... solvent ... acidic

Step-by-Step Solution

Answer

c

Step 1: Identify the Solvent

In an aqueous solution, water is typically the solvent. Therefore, in a can of cola, water is the solvent.

Step 2: Identify the Solute

The substance that is dissolved in the solvent is called the solute. In this case, sugar is dissolved in water, making sugar the solute.

Step 3: Determine the Nature of the Solution

The problem states that carbon dioxide makes the pH less than 7. A pH level less than 7 indicates that the solution is acidic.

Step 4: Choose the Correct Answer

Based on the analysis, the correct description is that water is the solvent, sugar is the solute, and carbon dioxide makes the solution acidic. Therefore, the correct answer is c.

Key Concepts

Solvent

In an aqueous solution, the solvent is the substance that dissolves other materials. Think of it as the medium in which the solutes are dispersed. In most everyday scenarios involving aqueous solutions, water is the most common solvent. For example, in a can of cola, water makes up the major part of the solution, acting as the solvent. When identifying the solvent, look for the component present in the largest quantity.

Solute

The solute is the substance that gets dissolved in the solvent. To put it simply, it's the minor component in a solution whose particles are uniformly distributed within the solvent. In our cola example, sugar is the solute because it is dissolved in water. Solutes can be solids, liquids, or gases, but they are always less abundant than the solvent. The solute's role significantly impacts the properties of the solution, including taste, color, and electrical conductivity.

pH Level

The pH level measures the acidity or basicity of a solution on a scale from 0 to 14. A pH less than 7 indicates an acidic solution, a pH of 7 is neutral, and a pH greater than 7 is basic (alkaline). In the case of cola, carbon dioxide dissolved in water forms carbonic acid, which decreases the pH making the solution acidic. Monitoring pH levels is crucial in various fields, such as chemistry, medicine, and environmental science, because it influences molecule behavior and chemical reactions.

Acidic Solution

An acidic solution has a pH level less than 7, meaning it contains more hydrogen ions \((H^+)\) than hydroxide ions \((OH^-)\). Acids can taste sour and can conduct electricity when dissolved in water. In our cola example, carbon dioxide gas dissolves in water to form carbonic acid, resulting in a pH less than 7. Acidity in solutions can affect their reactivity and interactions with other materials. Understanding solutions' pH is essential for predicting behavior in chemical processes and consumer products.