when a concentrated solution of an electrolyte is diluted
When a concentrated solution of an electrolyte is diluted, its specific conductance decreases but its equivalent (or molar) conductance increases.
Quick Scoop: What exactly changes?
Think of two different “kinds” of conductance:
- Specific conductance (κ) : Conductance of a unit volume of solution (e.g., 1 cm³).
- Equivalent/molar conductance (Λ) : Conductance due to one gram-equivalent or one mole of electrolyte in solution.
When you dilute:
- In each unit volume , there are fewer ions, so specific conductance drops.
- But the ions that are present are more free to move (less inter-ionic attraction, more dissociation especially for weak electrolytes), so equivalent/molar conductance rises.
So, the correct conceptual statement is:
When a concentrated solution of an electrolyte is diluted, its specific conductance decreases and its equivalent (or molar) conductance increases.
If this was an MCQ like:
- (a) specific conductance increases
- (b) equivalent conductance decreases
- (c) specific conductance decreases and equivalent conductance increases
- (d) both increase
Then the correct option is (c).
Why this happens (short story version)
Imagine a crowded hallway vs. a spacious one:
- In the crowded hallway (concentrated solution), there are many people (ions) per meter, but they bump into each other and can’t move freely.
- In the spacious hallway (dilute solution), there are fewer people per meter, but each person can walk faster and straighter.
Translated to electrolyte solutions:
- Dilution reduces the number of ions per unit volume → specific conductance ↓.
- Dilution reduces ion–ion interactions and increases dissociation , especially for weak electrolytes → each mole or equivalent of electrolyte conducts better → equivalent/molar conductance ↑.
Mini table: what goes up, what goes down?
Here’s the behavior in simple exam language:
| Quantity | Symbol | What happens on dilution? |
|---|---|---|
| Specific conductance | κ | Decreases (fewer ions per unit volume). | [7][2]
| Equivalent / molar conductance | Λ | Increases (ions move more freely; more dissociation). | [3][10][7]
Forum-style recap
Q: When a concentrated solution of an electrolyte is diluted, what changes?
A: Specific conductance decreases, equivalent (or molar) conductance increases. This is the standard result used in electrochemistry questions and MCQs.
TL;DR:
When a concentrated solution of an electrolyte is diluted, specific
conductance ↓, equivalent/molar conductance ↑.
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