Question

Which of the following(s) is/are true for the given elementary reaction?
$3A+\frac{1}{2}B+2C\to \frac{3}{2}X+2Y$

• A. Order of the reaction is $\frac{11}{2}$
• B. Rate law is
  $K\left[A{]}^3\right[B{]}^{\frac{1}{2}}[C{]}^2$
• C. Sum of stoichiometric coefficient is not equal to order of reaction
• D. Rate law is
  $K\left[X{]}^{\frac{3}{2}}\right[Y{]}^2$

Answer 1

Answer: (A), (B)

Rate law is

$K\left[A{]}^3\right[B{]}^{\frac{1}{2}}[C{]}^2$
For irreversible reaction, rate of reaction only depends on the concentration of reactants only. Generally they do not depend on product concentration.
Thus, the rate of reactioon is proportional to concentratiom of reactants.
The representation of rate of reaction in terms of the concentration of the reactants is called rate law.
$R=K(\text{Concentration}{)}^{\text{order}}$

Order of a reaction:
For a given reaction:
$aX+bY+cZ\to \text{Products}$
If,
$\text{Rate}\propto \left[X{]}^p\right[Y{]}^q[Z{]}^r$
Overall order of the reaction is :
$(p+q+r)$
$\text{Rate}=K\left[X{]}^p\right[Y{]}^q[Z{]}^r$

For elementary reaction (Reaction involves only single step):
The sum of stoichiometric coefficients is equal to the order of the reaction.
Thus, for
$3A+\frac{1}{2}B+2C\to \frac{3}{2}X+2Y$

Order of reaction is:
$3+\frac{1}{2}+2=\frac{11}{2}$

Rate law of reaction is
$R=K\left[A{]}^3\right[B{]}^{\frac{1}{2}}[C{]}^2$