Chemistry Experiment - Preparation of 5N HCl Solution - Introduction
Standard liquid solutions, like acids, are readily available and simple to prepare. By calculating the volume of the solution and diluting it in water into a volumetric flask with a known volume of solution, one can perform the preparation of the standard solution.
HCl is the chemical formula of hydrochloric acid. In this experiment with the given 12N concentrated HCl, the preparation of 250 ml of 5N HCl solution is explained in detail. HCl also acts as uncoloured gas and possesses a pungent smell. It turns into a colourless solution at 189 K and a white solid at 159 K when it freezes.
Table of Content
Aim
Procedure
Result
Aim
To prepare 250 ml of 5N HCl from the given 12N HCl.
Apparatus Required
250mL beaker
250mL Volumetric flask
Glass rod
Funnel
250mL measuring flask
Watch glass
Wash bottle
Theory
A standard solution is the one whose concentrations are precisely known. To prepare the 5N HCl solution, the volume of HCl solution required is prepared using the normality equation,
\[{N_1}{V_1} = {N_2}{V_2}\]
N1 is the normality of the concentrated HCl provided. \[{N_1} = 12N\]
V1 is the volume of the HCl required to prepare. \[{V_1} = ?\]
N2 is the normality of the HCl solution to be prepared. \[{N_2} = 5N\]
V2 is the volume of the HCl solution to be prepared. \[{V_2} = 250mL\]
\[12N \times {V_1} = 5N \times 250mL\]
\[{V_1} = \frac{{5N \times 250mL}}{{12N}}\]
\[{V_1} = 104.2mL\]
104.2mL concentrated HCl solution is required to prepare 250mL of 5N HCl solution.
Procedure
Preparation of 250mL of 5N HCl from the Provided 12N HCl
To prepare 5N 250 ml HCl, estimate how much 12N HCl is required.
Measure approximately 100 ml distilled water and pour it into a 250 ml beaker using a measuring cylinder. This water volume is a tiny bit less than the amount which will be necessary.
In a measuring cylinder, measure 104.2 ml of the provided concentrated HCl. To the water collected in the beaker, acid should be added slowly and carefully while stirring it with a glass rod. Occasionally run tap water over the beaker to cool it off.
After adding all the acid, pour the mixture from the beaker into a 250 ml volumetric flask using a glass rod and funnel.
Using a wash bottle, gently pour sufficient distilled water into the flask to fill it to just beneath the mark that has been carved on it.
When the lower layer of the meniscus almost reaches the line on the flask, add the final few millilitres of distilled water drop-wise using a pipette.
Put a stopper on the volumetric flask and give it a little shake to evenly distribute the solution. Mark it as a 5N HCl solution.
Observations
Result
The result of the chemistry experiment on the preparation of 250mL of 5N HCl from the given 12N HCl verified that:-
A 250 ml or 5N HCl solution has been successfully prepared.
Precautions
Handle chemicals and apparatus with caution.
Every apparatus should be rinsed with distilled water, and dried before starting the experiment.
The solution preparation should be done while wearing an apron.
Concentrated HCl should be added very slowly through continuous stirring in the water.
Use a measuring cylinder to collect the concentrated acid. Employ pipette filler if you must use a pipette. Avoid sucking through pipette.
To make the solution uniform, it must be thoroughly shaken.
If any acid spills on your body, immediately wash it off with water. Apply a little ointment after that.
After the completion of the experiment, wash your hands thoroughly.
Lab Manual Questions
1. Why should the solution be stirred continuously while pouring concentrated HCl into water?
Ans: This provides a consistent temperature rise across the entire solution. This prevents local heating, which would otherwise cause the glass vessel to shatter.
2. What is the aim of transferring solutions employing glass rod?
Ans: Solutions are poured using glass rods to prevent spillage. A glass rod placed against a beaker's pouring edge enables the solution to run down the glass rod and into the collecting vessel, as opposed to splashing beyond the lip.
3. Why does the pipette not blow out the final drop?
Ans: Due to surface tension, a tiny drop of liquid remains in the pipette after the last drop is added, preventing the last drop from being blown out. Furthermore, the design of pipettes ensures that this drop won't have an impact on the empirical value.
4. Why is it necessary to close the volumetric flask once the solution is prepared?
Ans: The solute's ability to interact with the moisture of the oxygen or absorb carbon dioxide or some additional pollutant in the air is dependent on the solute.
Viva Questions
1. Define normality?
Ans: The number of solute in a solution measured in gram or mole equivalents per litre is referred to as the normality.
2. What is the normality equation to calculate normality of HCl?
Ans: The normality equation is \[{N_1}{V_1} = {N_2}{V_2}\]
3. What does normality is used to indicate?
Ans: Hydroxide or hydronium ions concentration in a solution
4. What is the correct way of diluting an acid?
Ans: The correct way of diluting an acid is to add acid into water with constant stirring.
5. What kind of water is used for the preparation of HCl solution?
Ans: Distilled water is used for the preparation of HCl solution.
6. What is the base’s acidity
Ans: The acidity of the base is the number of replaceable hydroxide ions.
7. What is the acid's basicity?
Ans: Basicity of acid is the number of replaceable hydrogen ions.
8. Why should a pipette never be held by its bulb?
Ans: The glass bulb could expand due to body heat, which would cause a measuring inaccuracy.
9. What are the two types of standard solution?
Ans: Primary and secondary standard solution.
10. What is the symbol of normality?
Ans: Normality is denoted by the symbol N.
Practical-Based Questions
1. What is the unit of normality?
M or Moles L-1
N or eq L-1
Mol per kg
None of the above option
Ans: The unit of normality is N or eq L-1.
Choose the correct option for 1N HCl preparation?
6.33mL HCl in 100 L of water
7.33mL HCl in 100 L of water
8.33mL HCl in 100 L of water
9.33mL HCl in 100 L of water
Ans: For 1N HCl preparation for 100mL, 8.33mL HCl in 100 L of water should be added.
What is the standard of HCl solution?
Primary
Secondary
Territory
None of the three options
Ans: HCl is a secondary standard solution.
Why is HCl not considered the primary standard?
Stability
Concentration
Both concentration and stability
None of the three options
Ans: HCl solution is not considered as the primary standard due to both concentration and stability of the solution.
What type of instrument is used in this experiment to add the last drop to avoid the extra drops in the solution while transferring solution in volumetric flask?
Dropper
Wash bottle
Pipette
None of the above three option
Ans: Pipette is used to avoid extra drops during solution preparation
What type of acid is HCl?
Strong
Moderate
Weak
None of the above three option
Ans: HCl is a strong acid.
How is the strength of a particular solution determined?
Law of mass action
Equivalent law
Henry’s law
None of the three options
Ans: Equivalent law is used to determine the strength of a particular solution.
When was HCl prepared initially?
1648
1748
1848
1948
Ans: HCl solution was initially prepared in the year 1648.
How does distilled water act in chemical laboratories?
Indicator
Solvent
Universal solvent
None of the three options
Ans: Distilled water acts as a universal solvent in chemical laboratories.
What is the common name of HCl (hydrochloric acid)?
Ethanedioic acid
Caustic soda
Muriatic acid
Caustic potash
Ans: The common name of HCl is muriatic acid.
Conclusion
This Chemistry experiment on the preparation of 250mL of 5N HCl from the given 12N HCl infers that the hydrochloric acid is also known as muriatic acid. HCl is the chemical formula for hydrochloric acid. The concentration of the hydrochloric acid solution can be determined with high accuracy. A 5N HCl of 250mL solution is prepared by calculating the volume to be prepared using the provided 12N hydrochloric acid solution. It is prepared utilizing only pure chemicals and standardisation can be done to determine the precise concentration.
FAQs on Preparation of 250 ml of 5N HCl from the Given 12N HCl
1. What is the formula used to calculate the volume of 12N HCl required to prepare 250 ml of 5N HCl solution?
The formula used is N1V1 = N2V2, where N1 is the normality of concentrated HCl (12N), V1 is the volume of concentrated HCl required, N2 is the desired normality (5N), and V2 is the final volume of solution (250 ml).
2. List the important steps to safely prepare 250 ml of 5N HCl from 12N HCl in the laboratory.
- Estimate the required volume (104.2 ml of 12N HCl).
- Add about 100 ml distilled water to a beaker.
- Slowly add 104.2 ml concentrated HCl to the water with constant stirring.
- Transfer the mixture to a 250 ml volumetric flask.
- Add distilled water up to the mark, dropwise at the end.
- Close and shake the flask to mix thoroughly.
3. Why is it important to add acid to water, not water to acid, when preparing diluted HCl solutions?
Adding acid to water ensures that heat generated is absorbed by the larger water volume, reducing the risk of splattering and accidents. Adding water to concentrated acid can cause rapid boiling and splashes, making it unsafe during board lab exams.
4. What laboratory precautions must be strictly followed while preparing a standard solution of HCl for board practical exams?
- Always wear an apron and safety goggles.
- Handle concentrated acids with care and use a measuring cylinder or pipette (never mouth pipette).
- Stir continuously while diluting acid.
- Work in a well-ventilated area.
- Wash hands and apparatus thoroughly after the experiment.
5. Explain the difference between a primary and a secondary standard solution in the context of HCl preparation.
A primary standard solution is highly pure, stable, and has a known concentration, used to calibrate other solutions. HCl is a secondary standard as its concentration can change due to evaporation or reaction with air, so it requires standardisation before use in exams.
6. How can calculation mistakes impact the preparation of a 5N HCl solution, and what are the implications for board exam marks?
Calculation mistakes can lead to incorrect normality, affecting experiment results. In board practicals, such errors may result in loss of marks under accuracy, observation, and procedure headings, which are key for scoring full marks in Chemistry practicals (as per CBSE 2025-26 weightage).
7. What are common board exam traps when preparing questions on the dilution of strong acids like HCl?
- Confusing molarity with normality in calculations.
- Incorrectly applying the dilution formula.
- Ignoring safety steps when describing procedure.
- Misstating the direction of mixing acid and water.
Exam questions often assess these subtle traps.
8. Why is normality preferred over molarity in acid-base titrations, especially in board lab practicals involving HCl?
Normality (N) directly expresses the number of equivalent weights of solute per litre, making calculations in titrations simpler, especially when reactions involve multiple equivalents (like acids and bases exchanging protons), which matches the CBSE Chemistry practical syllabus focus.
9. What should you do immediately if concentrated HCl accidentally spills on your skin during experiment preparation?
Immediately wash the affected area with plenty of water and apply a mild ointment if irritation occurs. Reporting to the teacher and taking further medical advice is recommended. This is an important Chemistry exam safety point.
10. How can you verify the accuracy of your prepared 5N HCl solution in the laboratory?
Accuracy can be checked by titrating a known volume of the solution with a standard alkali, using a suitable indicator, and calculating the normality from the reaction. The result should closely match the intended 5N value, ensuring correctness for board practical marks.
11. What role does distilled water play in the preparation of laboratory acid solutions like HCl, according to CBSE practical requirements?
Distilled water ensures the solution is free from ions or contaminants that could interfere with reactions or affect normality. Using pure solvents is crucial to maintain accuracy in board practicals and to meet CBSE exam standards.
12. How are board examiners likely to test your understanding of the significance of accurately labeling standard solutions in the lab?
Examiners may ask why the volumetric flask must be labeled with the concentration (e.g., 5N HCl) and date. This proves solution identity and ensures only accurate, standardised solutions are used, which affects result reliability and scoring.
