How to Convert Molarity to Normality: Formula, n-Factor, and Examples
Relation between molarity and normality is essential in chemistry and helps students understand various practical and theoretical applications related to this topic. A clear grasp of this relationship is key for accurately preparing solutions, performing titrations, and mastering acid-base as well as redox reactions.
What is Relation Between Molarity and Normality in Chemistry?
The relation between molarity and normality in chemistry is about understanding two different units of solution concentration. Molarity (M) refers to the number of moles of solute present in one litre of solution. Normality (N) refers to the number of gram equivalents of solute per litre of solution.
This concept appears in chapters related to concentration of solutions, titration, and acids and bases, making it a foundational part of your chemistry syllabus.
Molecular Formula and Composition
While molarity and normality are not actual molecules, they are used to describe the amount of chemical components in a solution. Molarity measures how many moles (using molar mass) while normality measures equivalents (using equivalent mass or n-factor). Both are categorized as concentration units in physical chemistry.
Relation Between Molarity and Normality: Formula
The central formula that shows the relation between molarity and normality is:
Normality (N) = Molarity (M) × n-factor
Here, the n-factor depends on whether you are dealing with an acid (basicity = number of H+ ions), a base (acidity = number of OH− ions), a salt, or a redox-active compound (number of electrons exchanged).
Role and Calculation of n-factor
The n-factor decides how many equivalents are present in one mole of a substance. It varies by chemical reaction type:
- Acids: Number of replaceable H+ (example: H2SO4 → n = 2)
- Bases: Number of OH− ions (example: Ca(OH)2 → n = 2)
- Salts: Depends on total charge or group exchanged
- Redox: Number of electrons gained or lost per mole
Knowing how to calculate n-factor helps you use the molarity and normality formula correctly.
Step-by-Step Reaction Example
Let’s take a common chemistry example with sulphuric acid (H2SO4):
1. Suppose you have a 1M H2SO4 solution.2. The acid has basicity 2 (can donate 2 H+ ions), so n-factor = 2.
3. Using the formula: Normality = Molarity × n-factor
4. Normality = 1M × 2 = 2N
5. Final Answer: A 1 molar sulphuric acid solution is 2 normal.
Comparison Table: Molarity vs Normality
| Molarity (M) | Normality (N) |
|---|---|
| Moles of solute per litre of solution | Equivalents of solute per litre of solution |
| Unit: mol/L | Unit: eq/L |
| Depends only on amount of solute | Depends on reaction and n-factor |
| Formula: M = (moles)/(litre) | Formula: N = M × n-factor |
| Commonly used for general solutions | Preferred for titrations and redox reactions |
Frequent Related Errors
- Mistaking 1M for 1N without checking n-factor
- Using normality when molarity is asked (and vice versa)
- Forgetting to adjust normality when diluting a solution
- Selecting wrong n-factor (especially in redox titrations)
Uses of Relation Between Molarity and Normality in Real Life
The molarity and normality connection is widely used in titration experiments, making chemical calculations easier and more reliable. Industries use this relation for making correct formulations of acids, bases, and cleaning agents. In labs, accurate normality calculations help in pharmaceutical preparations and food analysis.
Relation with Other Chemistry Concepts
Understanding the relation between molarity and normality also helps you connect with topics like molality (a mass-based unit), titration analysis, and difference between molarity and normality. Mastery of these units makes all solution chemistry stronger.
Lab or Experimental Tips
Remember this trick: For strong acids and bases, normality can often be found by multiplying molarity by the number of H+ or OH− ions. Vedantu educators frequently remind students to double-check the n-factor in every calculation to avoid mistakes during titration labs.
Try This Yourself
- Calculate the normality of 1M Ca(OH)2 (acidity = 2).
- Is a 0.5N solution always 0.5M? Give an example.
- Find n-factor for Na2CO3 in an acid-base reaction.
- If you dilute 1L of 2N HCl to 2L, what is the final normality?
Final Wrap-Up
We explored relation between molarity and normality—why it matters, how to use its formula, step-by-step calculations, and common errors. For more in-depth notes and live explanations, visit Vedantu’s pages on molarity. This will help you gain full confidence in all concentration concepts!
FAQs on Relation Between Molarity and Normality in Chemistry
1. What is the relation between molarity and normality?
The relation between molarity (M) and normality (N) is:
Normality (N) = Molarity (M) × n-factor
The n-factor depends on the ion exchange or reactive capacity of the solute (such as the number of H+ ions for acids, OH− for bases, or electrons for redox reactions).
2. How do you convert molarity to normality?
To convert molarity (M) to normality (N):
- Multiply the solution’s molarity by the appropriate n-factor.
- Formula: Normality = Molarity × n-factor
- The n-factor depends on the substance and the type of reaction.
3. What is the n-factor in chemistry?
The n-factor is the number of equivalents contributed per mole of solute.
- For acids: Number of H+ ions donated
- For bases: Number of OH− ions donated
- For salts: Total charge on cation/anion
- For redox reactions: Number of electrons exchanged
It is crucial for calculating normality from molarity.
4. Is 1M the same as 1N for all solutions?
No, 1M equals 1N only if the n-factor is 1. For compounds where n-factor differs from 1, their molarity and normality will not be equal.
- Example: For H2SO4, 1M = 2N because its n-factor is 2.
5. What is the difference between molarity and normality?
Molarity (M): Moles of solute per liter of solution
Normality (N): Equivalents of solute per liter of solution
- Molarity depends only on the amount of solute.
- Normality depends on both the amount and the n-factor, which represents the number of reactive units (like H+, OH−, or electrons).
6. What is the normality of 1M H2SO4 solution?
The normality of 1M H2SO4 is 2N.
- Sulphuric acid (H2SO4) donates 2 H+ ions, so n-factor = 2.
- Normality = 1M × 2 = 2N.
7. Why is normality used in titrations?
Normality simplifies titration calculations because it directly measures equivalents exchanged in the reaction.
- It helps compare acids, bases, or redox agents regardless of their molecular mass.
- Especially useful when dealing with reactions involving multiple ion exchanges or electrons.
8. How do you find the n-factor for a compound?
To find the n-factor:
- Acids: Count H+ ions donated per molecule
- Bases: Count OH− ions accepted/donated per molecule
- Redox: Count electrons exchanged
Check the balanced reaction or compound formula to determine the correct value.
9. Can normality ever be less than molarity?
Yes, normality can be less than molarity if the n-factor is less than 1.
- This is uncommon but may happen in specific redox or disproportionation reactions where the equivalent factor per mole is below one.
10. What are common mistakes students make when converting between molarity and normality?
Common mistakes include:
- Forgetting to determine the correct n-factor
- Using the wrong n-factor for the type of reaction
- Assuming 1M = 1N for all solutions
- Ignoring the reaction context when choosing n-factor
Always review the reaction and double-check the n-factor before conversions.
11. How is normality calculated for mixtures containing multiple acids or bases?
For mixtures, normality is calculated by summing the equivalents of all components:
- Find the equivalents provided by each acid or base
- Add together the equivalents per liter
- Normality = (Total equivalents of all components) / (Total volume in liters)
12. Is normality always the preferred unit over molarity?
No, normality is not always preferred.
- It is mainly used for titrations and reactions involving equivalents.
- Molarity is more common for preparing solutions and general concentration calculations where n-factor is not needed.
