This laboratory session is structured into two significant segments aimed at enhancing understanding and practical skills in chemistry, particularly in solution preparation and acid-base property analysis.
The first part focuses on preparing diluted acid solutions using dilution techniques, teaching participants how to adjust solution concentrations by adding distilled water. This process is fundamental for creating samples with varying concentrations from concentrated stock solutions, highlighting the importance of precise concentration manipulation for diverse chemical applications.
The second part involves using a pH meter to measure the pH of the solutions prepared earlier, allowing an examination of their acid-base behavior, and understanding the impact of acid concentration on pH levels, thereby determining their acidity or basicity.
Educational Goals
- Solution Preparation Techniques: Participants will learn the basics of preparing solutions, including the critical practice of diluting concentrated solutions to achieve desired concentrations, emphasizing the significance of concentration control in chemistry.
- Understanding Acid-Base Behavior: Through pH measurement, students will explore how varying acid concentrations affect solution pH, gaining insights into the acidity or basicity of solutions.
- pH Measurement and Interpretation: The session aims to enhance skills in using pH meters for accurate pH determination and to develop the ability to interpret pH results, fostering a deeper comprehension of acidic and basic solution properties.
By participating in this laboratory, students will become familiar with essential chemistry practices, from manipulating solution concentrations to analyzing acid-base properties through pH measurement. Understanding how to adjust solution concentrations and measure their pH equips students with vital practical skills in chemistry, alongside a more profound understanding of acids and bases in solution. This comprehensive approach ensures a well-rounded educational experience, underlining the practical application of theoretical chemistry concepts in real-world scenarios.
Protocol
Part 1: Preparation of diluted solutions
Step 1: Identify the four beakers, numbered from 1 to 4.
Step 2: Pour 1.00 M acetic acid (CH3COOH) solution into beaker 1 until it is half full.
Step 3: Using a pipette, take 5.0 mL of the 1.00 M acetic acid solution from beaker 1 and transfer it to a 50 mL graduated cylinder.
Step 4: Add distilled water to the graduated cylinder until the final volume reaches 50 mL.
Step 5: Pour the solution from the graduated cylinder into beaker 2 until it is half full.
Step 6: Clean the pipette and graduated cylinder with distilled water.
Step 7: Repeat the dilution process by taking 5.0 mL of the solution from beaker 2, and dilute it to 50 mL with distilled water in the graduated cylinder.
Step 8: Transfer this new diluted solution into beaker 3 until it is half full.
Step 9: For beaker 4, fill it half with a 0.10 M hydrochloric acid (HCl) concentrated solution.
Part 2: Measurements
Step 10: Use a pH meter to measure the pH of each of the solutions contained in beakers 1 to 4.
Step 11: Between each measurement, rinse and dry the pH meter electrodes with distilled water.
Step 12: Consult and record your results in the table provided on the tablet.
Step 13: Properly dispose of the solutions used by pouring them into the designated waste container. Avoid disposing of them down the sink.
Anticipated Outcomes
- The beaker 1 contains CH3COOH 1M, and the pH is approximately 2.37.
- The beaker 2 contains CH3COOH 0.1M, and the pH is approximately 2.87.
- The beaker 3 contains CH3COOH 0.01M, and the pH is approximately 3.37.
The beaker 4 contains HCl 0.1M, and the pH is approximately 1.
Summary of Assignment by Grade Range
Grades 3-5 (Ages 8-10)
- Focus: Basic introduction to acid and base concepts and simple dilution.
- Activities: Observing changes in pH with simple dilution, basic demonstrations of strong and weak acids, basic safety instructions.
Grades 6-8 (Ages 11-13)
- Focus: Intermediate understanding of solution preparation and pH measurement.
- Activities: Preparing diluted acid solutions from concentrated stock, measuring pH with pH meters, observing the impact of dilution on pH, following detailed safety protocols.
Grades 9-12 (Ages 14-18)
- Focus: Advanced understanding of acid-base behavior, precise dilution techniques, and pH analysis.
- Activities: Accurately preparing various diluted acid solutions, using pH meters for precise pH measurement, analyzing the relationship between acid concentration and pH levels, detailed recording and interpretation of results, adhering to advanced safety protocols.
Laboratory essentials
Instruments
Beakers (50ml, 250ml & 1000ml)
Bucket plate
Droppers
Electronic Scale
Erlenmeyer (250ml)
Glass Rod
Graduated Cylinders (25ml & 100ml)
Hot plate
Magnetic stirrer
Paper towel
PH meter
Pipette
Spatulas
Test Tubes
Thermometers
Timer
Products
Ethanoic acid 1.0M (CH3COOH).
Hydrochloric acid (HCl).