Normality Calculator

Calculate normality and equivalent weight for acid-base and redox titration calculations

Calculation Mode

From Mass

Calculate normality from mass of solute

From Equivalents

Calculate normality from equivalents

Find Mass Needed

Calculate mass to prepare solution

Normality ⇄ Molarity

Convert between N and M

Reaction Type

Mass of Solute

Molecular Weight (MW)

g/mol

n-factor (equivalents per mole)

For acids: number of H⁺ ions

Volume of Solution

What is Normality?

Normality (N) is a measure of concentration equal to the gram equivalent weight per liter of solution. It represents the number of equivalents of solute per liter of solution. The concept of normality is particularly useful in acid-base chemistry and redox reactions because it directly relates to the reactive capacity of the solution.

Normality Formulas:

N = equivalents / Volume (L)

N = (mass / Equivalent Weight) / Volume (L)

N = M × n (where n = n-factor)

• N = Normality (eq/L or N)
• equivalents = Number of gram equivalents
• Equivalent Weight = Molecular Weight / n-factor
• n-factor = Number of equivalents per mole
• M = Molarity (mol/L)

Determining the n-factor

Reaction Type	n-factor Definition	Example
Acid	Number of H⁺ ions donated	H₂SO₄: n = 2
Base	Number of OH⁻ ions accepted	Ca(OH)₂: n = 2
Redox	Number of electrons transferred	KMnO₄ in acidic: n = 5
Salt	Total charge of cation or anion	Al₂(SO₄)₃: n = 6

Normality vs. Molarity

Property	Normality (N)	Molarity (M)
Definition	eq solute / L solution	mol solute / L solution
Units	eq/L or N	mol/L or M
Depends On	Reaction type (n-factor varies)	Only substance identity
Relationship	N = M × n	M = N / n
Best For	Titrations, redox, acid-base	General chemistry, modern usage
Modern Usage	Being phased out (IUPAC)	Preferred standard unit

⚠️ Important Note:

While normality is still used in some analytical laboratories and older textbooks, IUPAC (International Union of Pure and Applied Chemistry) recommends using molarity instead, as it is unambiguous and doesn't depend on reaction type. However, normality remains useful for titration calculations where equivalent relationships are important.

Common n-factor Examples

Acids

HCl (hydrochloric acid) n = 1
H₂SO₄ (sulfuric acid) n = 2
H₃PO₄ (phosphoric acid) n = 3
CH₃COOH (acetic acid) n = 1

Bases

NaOH (sodium hydroxide) n = 1
Ca(OH)₂ (calcium hydroxide) n = 2
Al(OH)₃ (aluminum hydroxide) n = 3
NH₃ (ammonia) n = 1

Oxidizing Agents (Redox)

KMnO₄ (acidic) n = 5
KMnO₄ (neutral/basic) n = 3
K₂Cr₂O₇ (dichromate) n = 6
H₂O₂ (hydrogen peroxide) n = 2

Reducing Agents (Redox)

FeSO₄ (ferrous sulfate) n = 1
Na₂S₂O₃ (sodium thiosulfate) n = 1
SnCl₂ (stannous chloride) n = 2
H₂C₂O₄ (oxalic acid) n = 2

Worked Examples

Example 1: Calculate Normality of H₂SO₄

Problem: What is the normality of a solution containing 4.9 g of H₂SO₄ (MW = 98 g/mol) in 1000 mL of solution?

Step 1: Determine n-factor
H₂SO₄ donates 2 H⁺ ions, so n = 2

Step 2: Calculate equivalent weight
Eq. Wt. = MW / n = 98 / 2 = 49 g/eq

Step 3: Calculate equivalents
Equivalents = mass / Eq. Wt. = 4.9 / 49 = 0.1 eq

Step 4: Calculate normality
N = equivalents / Volume (L) = 0.1 / 1 = 0.1 N

Answer: 0.1 N H₂SO₄ (or 0.05 M since N = M × 2)

Example 2: Mass Needed for Titration

Problem: How many grams of NaOH (MW = 40 g/mol) are needed to prepare 250 mL of 0.5 N solution?

Step 1: Determine n-factor
NaOH provides 1 OH⁻, so n = 1

Step 2: Calculate equivalents needed
Equivalents = N × V = 0.5 eq/L × 0.25 L = 0.125 eq

Step 3: Calculate equivalent weight
Eq. Wt. = MW / n = 40 / 1 = 40 g/eq

Step 4: Calculate mass
mass = equivalents × Eq. Wt. = 0.125 × 40 = 5 g

Answer: 5 g NaOH

Example 3: Normality to Molarity Conversion

Problem: A 1 N solution of H₃PO₄ has what molarity?

Step 1: Determine n-factor
H₃PO₄ can donate 3 H⁺ ions, so n = 3

Step 2: Use conversion formula
M = N / n

Step 3: Calculate molarity
M = 1 N / 3 = 0.333 M

Answer: 0.333 M H₃PO₄

Applications of Normality

Acid-Base Titrations

In titrations, normality simplifies calculations because N₁V₁ = N₂V₂ at the equivalence point, regardless of the specific acids or bases used.

Redox Titrations

Determining concentrations of oxidizing or reducing agents using the equivalence relationship based on electron transfer.

Water Hardness Analysis

Measuring total hardness (Ca²⁺ and Mg²⁺ ions) using EDTA titrations, often expressed in terms of normality.

Industrial Quality Control

Rapid analysis of acid/base strength in industrial processes, especially in older manufacturing protocols.

Pharmaceutical Analysis

Assaying drug purity and determining equivalents of active pharmaceutical ingredients in formulations.

Environmental Testing

Measuring acidity, alkalinity, and oxidizing capacity in water samples and environmental monitoring.

References

Normality calculations are based on classical analytical chemistry principles:

Note: While normality is still used in some analytical contexts, particularly for titrations and classical analysis, IUPAC recommends using molarity (mol/L) as the standard concentration unit because it is unambiguous and doesn't depend on the specific reaction. When using normality, always specify the n-factor or reaction context to avoid confusion. The calculator assumes complete reaction of all equivalents (e.g., complete dissociation for acids/bases).

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