FST Lab 4 (Determination of pH of different solutions using pH meter)

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OBJECT:

To determine the Ph of different solutions using the Ph meter. 

REQUIREMENTS:

  • pH Meter

  • Caliberator

  • Apple Juice

  • Coke

  • Glass Electrode

THEORY:

pH Definition: Measure of acidity or alkalinity on a scale from 0-14, with 7 being neutral.

Importance of pH in Food: The pH level of food and its impact on acid-base balance plays an important role in several areas of nutrition, including food safety and medical nutrition therapy. 

pH Meter: A pH meter is a scientific instrument that measures the hydrogen-ion activity in water-based solutions, indicating its acidity or alkalinity expressed as pH.

Principle of pH Meter: Potentiometric pH meters measure the voltage between two electrodes and display the result converted into the corresponding pH value.

Applications of pH Meter: pH meters are used for soil measurements in agriculture, water quality for municipal water supplies, swimming pools, environmental remediation; brewing of wine or beer; manufacturing, healthcare and clinical applications such as blood chemistry; and many other applications.

Calibration of Ph meter. Why is it important? 

Calibration of pH meter is important to ensure accurate and reliable measurements.

PROCEDURE:

  • Turn on the pH Meter. Lift up the electrode and clean the electrode tip by pressing it with tissue paper.

  • Calibrate using buffer 4.0, buffer 7.0.

  • The buffers should come to room temperature before calibration. 

  • Place the electrode in the solution to know the pH.

  • Measure the pH of each solution using the Ph meter.

  • Rinse the tip of the probe with distilled water before putting the probe into each sample. 

  • Record your data in the observation table. 


OBSERVATIONS:

Sample

pH value using pH meter 

Standard pH

Apple Juice

1.62

3

Coke

1.12

2.53








RESULT: 

⦁The pH of the apple juice is 1.62 which is acidic.

⦁The pH of the coke is 1.12 which is acidic.

DISCUSSION:  

The purpose of our experiment is to determine the pH of various food samples using a pH meter. pH measures the potential of hydrogen in a solution, indicating its acidity or alkalinity. A pH meter is an instrument designed to measure the hydrogen ion activity in a solution. It operates on the principle of Potentiometry, which involves measuring the electric potential (voltage) of a solution.

In our results, we found that the pH of apple juice is 1.63, indicating it is highly acidic. However, the standard pH range for apple juice is typically between 3.0 and 4.5. Similarly, our experiment showed that the pH of Coke is 1.12, also very acidic, while the standard pH range for Coke is 2.6 to 2.7. We experienced some fluctuations during calibration, which could be attributed to machine error or human error.


Study questions: 

Q1) What is a buffer solution?

Ans: A buffer is a solution that can resist pH change upon the addition of an acidic or basic component. 

Q2) What are the factors affecting the Ph of food samples?

Ans: Time, temperature, nutrients, water, and salinity.

Q3) Why do you need to calibrate the pH meter with a standard pH buffer solution before pH measurement?

Ans: Because it helps ensure accurate and reliable results and allows it to accurately measure the acidity or alkalinity of a solution.

Q4) Give an example of acidic and basic buffer solutions.

Ans: Acidic buffer example: Mixture of acetic acid and sodium acetate.

  Basic buffer example: Mixture of ammonium hydroxide and ammonium chloride.

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