Normality Calculator
Calculate the normality of a solution from mass, equivalent weight, and volume, or convert between normality and molarity.
🧪 Normality Calculator
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What Is Normality?
Normality (N) is a measure of solution concentration that expresses the number of equivalents of solute per liter of solution. It is particularly useful in acid-base chemistry, redox reactions, and precipitation reactions because it directly relates to the reactive capacity of a substance.
Or equivalently:
Normality Formula
The basic formula for normality is:
Where:
- N — Normality (eq/L or N)
- m — Mass of solute (g)
- Ew — Equivalent weight of solute (g/eq)
- V — Volume of solution (L)
The equivalent weight is related to molar mass by:
And normality relates to molarity by:
What Is the n-factor?
The n-factor (or equivalence factor) depends on the type of reaction:
| Reaction Type | n-factor | Example |
|---|---|---|
| Acid-base | Number of H+ or OH− exchanged | H2SO4: n = 2 |
| Redox | Number of electrons transferred | KMnO4 in acidic: n = 5 |
| Precipitation | Total charge of cation or anion | CaCl2: n = 2 |
Equivalent Weights of Common Substances
| Substance | Molar Mass (g/mol) | n-factor | Eq. Weight (g/eq) |
|---|---|---|---|
| HCl | 36.46 | 1 | 36.46 |
| H2SO4 | 98.08 | 2 | 49.04 |
| H3PO4 | 98.00 | 3 | 32.67 |
| NaOH | 40.00 | 1 | 40.00 |
| Ca(OH)2 | 74.09 | 2 | 37.05 |
| KOH | 56.11 | 1 | 56.11 |
| Na2CO3 | 106.00 | 2 | 53.00 |
| KMnO4 (acidic) | 158.03 | 5 | 31.61 |
4.9 g of H2SO4 is dissolved in 500 mL of solution.
Step 1: Equivalent weight = 98.08 / 2 = 49.04 g/eq
Step 2: N = 4.9 / (49.04 × 0.5) = 4.9 / 24.52 = 0.2 N
Normality vs. Molarity
| Property | Normality (N) | Molarity (M) |
|---|---|---|
| Unit | eq/L | mol/L |
| Based on | Equivalents | Moles |
| Depends on reaction? | Yes (n-factor changes) | No |
| Relationship | N = M × n-factor | |
| For HCl (n=1) | 1 N = 1 M | Same |
| For H2SO4 (n=2) | 1 N = 0.5 M | Different |
Applications of Normality
- Acid-base titrations: NaVa = NbVb simplifies titration calculations.
- Water chemistry: Hardness, alkalinity, and acidity are often expressed in meq/L (milliequivalents per liter).
- Clinical chemistry: Electrolyte concentrations in blood (Na+, K+, Cl−) are reported in meq/L.
- Redox titrations: Normality accounts for electron transfer, making stoichiometry simpler.
Frequently Asked Questions
Is normality the same as molarity?
Only when the n-factor is 1 (e.g., HCl, NaOH). For polyprotic acids or polybasic bases, normality = molarity × n-factor. A 1 M H2SO4 solution is 2 N because each molecule provides 2 H+ ions.
Why is normality used less often today?
IUPAC has recommended against using normality because the n-factor depends on the specific reaction context. The same solution can have different normalities in different reactions. Molarity is unambiguous. However, normality remains widely used in analytical chemistry, water treatment, and clinical labs.
What is a milliequivalent (meq)?
A milliequivalent is 1/1000 of an equivalent. It is commonly used in clinical medicine (e.g., serum potassium = 3.5–5.0 meq/L) and water chemistry (hardness in meq/L).