The equivalent mass of a solute is the mass that will react with or replace one mole of hydrogen ions (H⁺) or hydroxide ions (OH⁻), or one mole of electrons in a redox reaction.
According to the reference, the equivalent mass of a solute is calculated as:
Equivalent mass of solute = (Molar mass of solute) / (n-factor of solute)
Here’s a breakdown:
- Molar Mass of Solute: This is the mass of one mole of the solute, typically measured in grams per mole (g/mol). You can find this value on the periodic table.
- n-factor of Solute: This value depends on the type of chemical species the solute is in the solution and how it interacts chemically. It could involve:
- Acids: The number of replaceable hydrogen ions (H⁺).
- Bases: The number of replaceable hydroxide ions (OH⁻).
- Salts: The total positive or negative charge of the cation or anion.
- Oxidizing/Reducing Agents: The number of electrons gained or lost in the redox reaction.
Understanding the n-factor
Determining the n-factor is crucial for calculating the equivalent mass. Here's how to approach it for different solute types:
Examples
- Acids:
- Hydrochloric Acid (HCl): n-factor = 1 (one replaceable H⁺ ion)
- Sulfuric Acid (H₂SO₄): n-factor = 2 (two replaceable H⁺ ions)
- Bases:
- Sodium Hydroxide (NaOH): n-factor = 1 (one replaceable OH⁻ ion)
- Calcium Hydroxide (Ca(OH)₂): n-factor = 2 (two replaceable OH⁻ ions)
- Salts:
- Sodium Chloride (NaCl): n-factor = 1 (total charge of Na⁺ or Cl⁻ is 1)
- Calcium Chloride (CaCl₂): n-factor = 2 (total charge of Ca²⁺ is 2 or 2 Cl⁻ equals to 2)
- Aluminum Sulfate (Al₂(SO₄)₃): n-factor = 6 (total positive charge of 2 Al³⁺ is 6 or total negative charge of 3 SO₄²⁻ is 6)
Importance
The equivalent mass is fundamental in calculations for:
- Titration: Determining the concentration of a solution.
- Neutralization Reactions: Finding the stoichiometric amounts of reactants.
- Redox Reactions: Understanding electron transfer.
By applying the formula and understanding the n-factor, one can calculate the equivalent mass of any given solute.
