In a reaction, compounds a and b combine to form compounds c and
d. the rate law is: rate = k[a][b]. what is the rate order?

Answer : The rate order of reaction is, second order reaction.

Explanation :

Rate of reaction : It is defined as the rate of change in concentration of reactant or product with respect to time.

Order of reaction : It is defined as the sum of the exponents or powers to which the molar concentration in the rate law equation are raised to express the observed rate of reaction.

As per question the reaction will be :

The given rate expression is,

From this expression we conclude that the power of concentration of reactant A and B are 1, 1.

The sum of power of concentration of reactant A and B = 1 + 1 = 2

That means it is a second order reaction.

Hence, the rate order of reaction is, second order reaction.

the correct answer is:

a. formation of precipitation