Problem 84 - Intermediate Algebra

Question

Chemistry. The pH scale is used to measure the strength of acids and bases (alkalines). It can be thought of as a number line. On the scale, graph and label each pH measurement given below. $$ \begin{array}{|l|r|} \hline \text { Solution } & \mathrm{pH} \\ \hline \text { Seawater } & 8.5 \\ \hline \text { Cola } & 2.9 \\ \hline \text { Battery acid } & 1.0 \\ \hline \text { Milk } & 6.6 \\ \hline \text { Blood } & 7.4 \\ \hline \text { Ammonia } & 11.9 \\ \hline \text { Saliva } & 6.1 \\ \hline \text { Oven cleaner } & 13.2 \\ \hline \text { Black coffee } & 5.0 \\ \hline \text { Toothpaste } & 9.9 \\ \hline \text { Tomato juice } & 4.1 \\ \hline \end{array} $$

Step-by-Step Solution

Answer

Plot each solution's pH on a number line from 0 to 14 and label them.

Step 1: Understanding the pH Scale

The pH scale ranges from 0 to 14, where values less than 7 indicate acidic solutions, values greater than 7 indicate basic (alkaline) solutions, and a value of 7 is neutral.

Step 2: Identify the pH Values to Plot

List the given solutions and their corresponding pH values: Seawater (8.5), Cola (2.9), Battery acid (1.0), Milk (6.6), Blood (7.4), Ammonia (11.9), Saliva (6.1), Oven cleaner (13.2), Black coffee (5.0), Toothpaste (9.9), Tomato juice (4.1).

Step 3: Plot and Label the Points on the pH Scale

Sketch a number line ranging from 0 to 14. Plot each solution at its respective pH value on this number line and label them accordingly. Each point represents the acidity or basicity of the solution.

Key Concepts

Acidic Solutions

Acidic solutions have a pH that is less than 7. This means they have a higher concentration of hydrogen ions (H⁺) compared to hydroxide ions (OH⁻). Some common everyday acidic solutions include items like cola, which has a pH of 2.9, and battery acid, which is very acidic with a pH of 1.0.
These solutions are often sharp in taste and can be corrosive to metals. The lower the pH value, the stronger the acid. Examples of acids?

• Lemon juice
• Vinegar
• Stomach acid

Remember, handling strong acids requires caution due to their potentially damaging effects.

Basic Solutions

Basic solutions, also referred to as alkaline solutions, have a pH greater than 7. Unlike acidic solutions, they have more hydroxide ions (OH⁻) than hydrogen ions (H⁺).
Their pH value indicates the degree of basicity - the higher the value, the more basic the solution is.
Common household basic solutions include:

• Seawater with a pH of 8.5
• Household ammonia at 11.9
• Oven cleaner, which is highly basic with a pH of 13.2

These solutions often feel slippery or soapy to the touch and can neutralize acids. They can also be harmful if not handled with care.

Neutral pH

A neutral pH is exactly 7. This point on the pH scale signifies a perfect balance between hydrogen and hydroxide ions, neither acidic nor basic.
Though pure water is the classic example of a substance with a neutral pH, in real-world settings like blood, a slightly different environment exists though it is close with a pH of 7.4.
Neutral solutions are pivotal in chemical reactions and biological systems.

• Maintains homeostasis in living organisms
• Supports non-intrusive reactions

A neutral environment often acts as a starting point for many laboratory experiments.

Chemical Properties

The chemical properties of a solution, often viewed through the lens of pH, dictate how it interacts with other substances. Whether a solution is acidic, neutral, or basic affects its role in chemical reactions.
Consider acidic and basic solutions:

• Acidic solutions can donate protons to other substances.
• Basic solutions can accept protons, reacting with acids to balance the pH.
• Neutralization is a reaction that transforms an acid and a base into water and salt.

This interaction understanding is essential in predicting chemical behavior and ensuring safety in chemical handling.

Number Line Representation

The pH scale is a continuous number line ranging from 0 to 14. Each unit change on the scale represents a tenfold difference in hydrogen ion concentration.
Visualizing pH on a number line makes it easier to understand the relative strength and weakness of solutions.

• Values from 0 to 6.9 indicate acidic solutions.
• Exactly 7 is neutral.
• Values from 7.1 to 14 signal basic solutions.

This pictorial representation helps in quickly identifying the acid-base nature of a solution, whether in a classroom setting or practical laboratory work.