Chemical Kinematics is a branch of physical chemistry that deals with determination of rate of reaction. A reaction proceeds with disappearance of a reacants and formation of products. So, the rate of a chemical reaction can be measured in terms of rate of disappearance of reactants and formation of products.
= mols litre-1 time -1
A + B → C
Rate of reaction can be measured in terms of rate of disappearance of A and B and rate of formation of C.
Note: -ve sign is used in change in concentration of reactant to make rate of reaction positive.