Q16.24 P - Chemistry: Molecular Nature Of Matter And Change

Question

To determine its rate law. Assuming that you have a valid experimental procedure for obtaining [A2] and [B2] at various times, explain how you determine 

${\mathbf{A}}_{\mathbf{2}\mathbf{\left(}\mathbf{g}\mathbf{\right)}}\mathbf{+}{\mathbf{B}}_{\mathbf{2}\mathbf{\left(}\mathbf{g}\mathbf{\right)}}\mathbf{\to }\mathbf{2}\mathbf{AB}\mathbf{\left(}\mathbf{g}\mathbf{\right)}$

(a) the initial rate, 

(b) the reaction orders, and 

(c) the rate constant. 

Step-by-Step Solution

Answer

1. At t = 0, the starting rate equals the negative slope of the reactant concentration versus time curve.
2. The influence of reactant concentration on reaction rate is determined by the reaction order.
3. The rate of constant is determined as  $$\begin{gathered} rate=k{\left[A_2\right]}^m{\left[B_2\right]}^n \\ k=\frac{rate}{{\left[A_2\right]}^m{\left[B_2\right]}^n} \end{gathered}$$ 

Step 1: (a) How to determine the initial rate

Plot the $\left[{\text{A}}_2\right]$and  $\left[B_2\right]$ graphs against time. The slope of the line tangent to the curve at t=0 s may be used to calculate the starting rate.

 

Step 2: (b) How to determine the reaction orders

The influence of reactant concentration on reaction rate is determined by the reaction order. Different beginning rates are determined by a series of tests at a constant temperature with various initial concentrations. When the starting concentration of a single reactant is modified, the results are compared, and the reaction order with regard to that reactant is determined. To identify the order of each reactant, the method is repeated for the following reactant.

Step 3: (c) How to determine the rate constant

Using the values of m and n, the rate law for the reaction is obtained:

$rate=k{\left[A_2\right]}^m{\left[B_2\right]}^n$

Where m and n denote the reaction order in relation to [A] and [B], respectively, to acquire the values of k, the values of reaction rate and concentrations from a successful experiment are substituted.

$$\begin{gathered} rate=k{\left[A_2\right]}^m{\left[B_2\right]}^n \\ k=\frac{rate}{{\left[A_2\right]}^m{\left[B_2\right]}^n} \end{gathered}$$