College of Engineering- Department of Civil Engineering
GROUP 5
Members:
Amponin, Jhon Rey
De Guia, Shereelou
Delos Santos, Justine
Macalalad, Angelene D.
Ricero, Suzanie A.
PRE LAB
ACIDITY
I.
INTRODUCTION
Acidity is a chemical property that characterizes the concentration of hydrogen
ions in a solution. Acidity in water in essence arises from the presence of dissolved acidic
compounds. These compounds can lead to the decrease in the water’s pH which indicates
its acidic nature.
II. MATERIALS:
Apparatus
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Analytical Balance
Burette with stand
Beaker (10 ml)
Dropper (provided)
Volumetric Flask
Conical Flask
Funnel
Magnetic Stirrer (if available)
Magnetic Bar (if available)
Chemical and Reagents
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III.
NaOH Solution (available in lab)
Methyl Orange Indicator (provided)
Distilled Water (not provided)
Water Sample (needed: 10ml)
COSTING
College of Engineering- Department of Civil Engineering
QUANTITY
MATERIAL
COST
1
METHYL ORANGE
INDICATOR
216
6
DROPPER
₱8.00 x 6 (48)
CONTRIBUTION:
TOTAL COST
30
= 264
30
Total Contribution=8.8 or 9 pesos (each)
IV.
PROCEDURES:
1. Preparation:
1.1. Set up a clean and dry workspace.
1.2. Ensure that the burette, conical flask, and other glassware are clean and free from any
contaminants.
2. Prepare the 1N NaOH solution:
2.1. Get the analytical balance and put the petri dish on it.
2.2. Weigh 4 grams of sodium hydroxide using the analytical balance.
2.3. Add the weighted NaOH to the 1-liter volumetric flask.
2.4. Pour 400 mL of distilled water into the flask. It is only an initial volume to ensure that
the solution dissolves completely.
2.5. After the NaOH has dissolved completely, add more distilled water to the flask until the
volumetric flask reaches the 1-liter mark.
College of Engineering- Department of Civil Engineering
3. Measuring the Water Sample:
3.1. Using a graduated cylinder or a measuring pipette, carefully measure 10 ml of the
water sample and transfer it to a clean and dry beaker.
4. Adding Methyl Orange Indicator:
4.1. Using a dropper, add 2 to 3 drops of 1% Methyl Orange indicator solution to the water
sample in the beaker. Swirl gently to mix.
5. Transfer to Conical Flask:
5.1. Carefully the solution from the beaker into a clean conical flask.
6. Preparing the Burette:
6.1. Place the burette in a burette stand.
6.2. Using a funnel, fill the burette with the 0.1 normal NaOH solution until the zero point.
Ensure that the burette is completely filled, and there are no air bubbles in the tip.
7. Titration Process:
(A) Setting Up Magnetic Stirring:
7.1. Place a magnetic stirrer below the burette.
7.2. Carefully place a magnetic bar into the conical flask containing the water sample and
indicator.
7.3. Power on the magnetic stirrer to ensure uniform mixing of the solution.
7.4. Open the stopcock of the burette to allow a controlled flow of the NaOH solution.
7.5. Continue adding the NaOH solution until the color of the solution turns pink. The pink
color indicates that the water has reached neutral pH.
(B) Manual Swirling:
7.1. In case of the absence of the magnetic stirrer at the laboratory, simultaneously swirl
the flask manually with your hand.
7.2. Open the stopcock of the burette slightly to allow a slow and controlled flow of the
NaOH solution.
7.3. Add the NaOH solution dropwise into the conical flask containing the water sample.
Swirl the flask gently after each drop.
7.4. Continue adding the NaOH solution until the color of the solution in the conical flask
changes from its initial color to pink. The pink color indicates that the water has reached
neutral pH.
8. Stopping the Titration:
8.1. As soon as the pink color appears and persists for about 30 seconds, immediately
close the stopcock of the burette to stop the flow of NaOH solution.
9. Recording the Reading:
College of Engineering- Department of Civil Engineering
9.1. Carefully read and record the initial and final burette readings. The difference between
these readings represents the volume of NaOH solution required to neutralize the acidity in
the water sample.
9.2. You can use this as a guide for the readings;
Volume of water Sample(V): 10 ml Consumed titrant (a): (?) ml Normality of NaO(N): 0.1 N
V.
FORMULA TO USE:
Calculating Acidity:
Acidity =
VI.
𝑁•𝑎
𝑉
• 1, 000 𝑚 𝑚𝑜𝑙/𝑙
GUIDE QUESTIONS:
1. What observations did you make?
2. What are the differences you noticed between the water samples and how they reacted to
the different solutions?
3. How can sources of error in the titration process be identified and addressed to improve
the accuracy and precision of the results?
4. How can the titration data be interpreted to draw conclusions about the properties of the
substances involved in the experiment?