Which of the following is a true statement about order of a reaction?

It is always equal to total stoichiometric number of reactants. It cannot be zero. It is an experimentally determined quantity. It can be easily predicted theoretically.

It is an experimentally determined quantity.

Order of a reaction is an experimentally determined quantity and it cannot be written from the balanced chemical equation (except for elementary reactions). It may be zero, whole number, fraction or negative.