Question

(i) What do you understand by velocity of a chemical reaction?
(ii) Explain Raoult’s law.

Hint:

Reaction rate measures speed of reaction; Raoult’s law explains colligative properties.

Answer 1

(i) Velocity of reaction.
The velocity (rate) of a chemical reaction is the change in concentration of reactants or products per unit time. \[ \text{Rate} = -\frac{d[\text{Reactant}]}{dt} = \frac{d[\text{Product}]}{dt} \] (ii) Raoult’s law.
According to Raoult’s law, for a solution of non-volatile solute: \[ \frac{\Delta p}{p^0} = x_{\text{solute}} \] where \(\Delta p = p^0 - p\), \(p^0\) = vapour pressure of pure solvent, \(x_{\text{solute}}\) = mole fraction of solute.
Step 3: Conclusion.
- Reaction velocity = rate of change of concentration.
- Raoult’s law = vapour pressure lowering proportional to solute mole fraction.