Classification of reaction:- (On the basis of rate (speed))

1. Very fast reaction:- Which takes place instantaneously or in a fraction of second (10^-12 to 10^-16 second)

e.g. → Ionic reaction:- AgNo₃ + Nacl → Agcl + NaNo₃

                                             NaoH + Hcl → Nacl + H₂O  

2. Very slow reaction:- Which takes few hours, days or months.

e.g. → Rusting of iron, formation of fossil fuels

3. Moderate reaction:- Reaction which are neither very slow nor very fast, they takes few seconds to few months

e.g. → Hydrolysis of sucrose

C₁₂ H₂₂ O₁₁ + H₂OC₆ H₁₂ O₆ + C₆ H₁₂ O₆

Sucrose                        Glucose       fructose

Question:- Why different reaction have different rates

Answer:- Every reaction involves breaking and making of bonds different bond require different amount of every for breaking and different amount of energy evolved when new bonds are formed during reaction. So rate of reaction of different reaction is different.