BIOS 251 Week 2 Lab Instructions Chemistry Basics

BIOS 251 Week 2 Lab Instructions Chemistry Basics

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Chamberlain University

BIOS-251 Anatomy & Physiology I

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Understanding pH Measurement and Chemical Solutions in Laboratory Settings

In this article, we will explore the basic chemistry principles tested in a Week 2 laboratory, focusing on pH measurement techniques, the role of buffers, acid-base reactions, and the preparation of chemical solutions. Understanding these principles is essential for students in biology, chemistry, and healthcare fields, where accurate chemical analysis is critical for various applications.

pH Measurement Techniques: Using pH Strips vs. pH Meters

Part A: Measuring pH Using pH Strips

One of the primary techniques used to determine the pH of a solution is the use of pH strips. These strips are coated with chemicals that change color depending on the pH level of the solution they are immersed in. In this experiment, we test several common household solutions, including distilled water, lemon juice, bleach, and two unknown solutions.

• Method: To begin, you will dip the pH strips into each solution and compare the resulting color change with a reference chart to estimate the pH.
• Results: This method provides a quick and easy way to determine whether a solution is acidic (pH below 7) or basic (pH above 7). Distilled water, for example, has a neutral pH of around 7, while lemon juice typically has a pH between 2 and 3, indicating a strong acid.

Part B: Measuring pH with a pH Meter

While pH strips are useful for rough estimations, a pH meter offers a more precise measurement. This electronic device can measure the concentration of hydrogen ions (H⁺) in a solution, providing an accurate pH reading.

• Method: The pH meter is dipped into the same solutions tested with the strips. The readings are recorded to compare with those obtained from the pH strips.
• Conclusion: This method allows for more accurate determination of a solution’s pH, confirming whether it is acidic, neutral, or basic.

The Role of Buffers in Chemical Reactions

Buffers are crucial in maintaining stable pH levels in various biological and chemical systems. In Part C, we explore how buffers resist changes in pH when exposed to strong acids, specifically by testing the effect of hydrochloric acid (HCl) on a phosphate buffer.

• Experiment: A dropwise addition of HCl to both distilled water and a phosphate buffer reveals the distinct properties of buffers. While the pH of the water quickly drops as acid is added, the phosphate buffer maintains a relatively stable pH.
• Key Observation: Buffers, like phosphate, are essential in biological systems, such as maintaining the pH of blood, where a slight deviation from the neutral pH of 7.4 can lead to health issues.

Neutralization Reactions: Comparing Antacids

In Part D, the focus shifts to acid-base neutralization reactions, a common phenomenon in many chemical processes, including the treatment of heartburn. In this experiment, we compare the neutralizing power of two popular antacids, Tums and Alka-Seltzer, using simulated stomach acid (0.36 M HCl).

• Method: To determine the effectiveness of each antacid, Tums and Alka-Seltzer are added to separate beakers containing stomach acid. The pH is measured after each tablet is added until the solution reaches a neutral pH of 7.
• Analysis: The total number of tablets required to neutralize the acid is recorded, and the active ingredients of each antacid are analyzed to determine which one is more efficient in neutralizing stomach acid.

Preparing Solutions and Their Concentration

Understanding the preparation of solutions is fundamental to many laboratory processes. Part E reviews the preparation of a normal saline solution, commonly used in medical settings for fluid delivery. The saline solution consists of sodium chloride (NaCl) dissolved in water, and the concentration of the solution is vital for its proper use.

• Method: To prepare a 500 ml bag of normal saline, 4.5 grams of NaCl are dissolved in water to make a 0.154 M solution. This solution is then sterilized by heating.
• Questions: You will calculate the concentration of this solution in terms of mass/volume percentage and determine its osmolality. Additionally, you’ll consider the effects of evaporation on the solution’s concentration during sterilization.

Reflection on Key Laboratory Concepts

After completing this lab, students should reflect on the following four key concepts learned:

1. Understanding pH and its measurement: The difference between pH strips and pH meters, and how each method is used to measure the acidity or basicity of a solution.
2. The role of buffers in biological systems: How buffers prevent drastic pH changes and maintain homeostasis, especially in the human body.
3. Neutralization reactions: The interaction between acids and bases, as demonstrated by the neutralization of stomach acid with antacids.
4. Solution preparation and concentration calculations: The importance of accurately preparing chemical solutions and understanding their concentrations for practical applications in healthcare.

Conclusion

This lab experience provides valuable insights into basic chemistry concepts, including pH measurement, the role of buffers, acid-base neutralization, and solution preparation. These concepts are not only fundamental to chemistry but also have significant applications in biology and medicine, particularly in maintaining pH balance in the body and preparing essential solutions for medical use.

BIOS 251 Week 2 Lab Instructions Chemistry Basics

By conducting these experiments, students will gain hands-on experience with various chemical techniques and deepen their understanding of how chemistry affects both the natural world and human health.