Definitions [4]
Define the term Catalysis.
The phenomenon of increasing the rate of a chemical reaction with the help of a catalyst is known as catalysis.
Define the term Inhibition.
The phenomenon in which the rate of a chemical reaction is reduced by an inhibitor is called inhibition.
A catalyst is a substance that alters the rate of a chemical reaction without being consumed. The phenomenon is called catalysis.
Emulsions are colloidal solutions of two immiscible liquids in which one liquid acts as the dispersed phase and the other as the dispersion medium.
Key Points
| Type | Description |
|---|---|
| Homogeneous |
Reactants and catalyst are in the same phase \[\ce{\underset{}{2SO2(g) + O2(g)} ->[NO(g)][]\underset{}{2SO3(g)}}\] |
| Heterogeneous |
Reactants and catalyst are in different phases \[\ce{\underset{}{N2(g) + 3H2(g)} ->[][Fe(s)]\underset{}{2NH3(g)}}\] |
| On the basis of the mechanism of catalysis: |
|
| Positive catalysis | Catalyst enhances the rate of reaction |
| Negative catalysis | Catalyst retards the rate of reaction |
| Auto-catalysis | One of the products acts as catalyst |
| Induced catalysis | One reaction induces the rate of another reaction |
Emulsions show all properties of sols. Their particle size is 1000 Å to 10,000 Å; they scatter light (Tyndall effect).
Types of Emulsions:
| Feature | Oil in Water (O/W) | Water in Oil (W/O) |
|---|---|---|
| Dispersed phase | Oil | Water |
| Dispersion medium | Water | Oil |
| Continuous phase | Water | Oil |
| Miscibility | Addition of water mixes with it | Addition of oil mixes with it |
| Electrolyte effect | Small amount makes it conducting | No effect on conducting power |
| Emulsifiers used | Water-soluble alkali metal soaps, metal sulphates | Water-insoluble soaps (Zn, Al, Fe), alkaline earth metal soaps |
| Examples | Milk, vanishing cream | Butter, cream, cod liver oil |
