Question

what are various method for determination of order of reaction​

Answer 1

Answer:

Initial Rate Method.

Graphical Method.

Half Life Method.

Van't Hoff Differential Method.

Related Resources.

Explanation:

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Answer 2

Answer:

there u go....hope it hhelps

Explanation:

Initial Rate Method

In this method initial rate of reaction is determined by varying the concentration of one of the reactants while others are kept constant

R = k[A]x[B]y[C]z

if [B] & [C] = Constant

then for two different initial concentrations of A we have

R_{0_1} = k[A_0]^{a}_{1}

and

R_{0_2} = k[A_0]^{a}_{2}

\Rightarrow \frac{R_{0_1}}{R_{0_2}} = (\frac{[A_0]_1}{[A_0]_2})^n

Graphical Method

This method can be used when there is only one reactant.

If the plot of log [A] vs t is a straight line, the reaction follows first-order .

If the plot of 1/[A] vs t is a straight line, the reaction follows second order.

If the plot of 1/[A]2 is a straight line , the reaction follows third order.

Generally, for a reaction of nth order, a graph of 1/[A]n-1 vs t must be a straight line.  

Here [A] is the concentration of reactant at any given time of the reaction (other t =0). [A] = (a-x) where a is the initial concentration  and x is the extent of reaction at time t.

Refer to the following video for Determination of Order of a Reaction  

Half Life Method

This method is used only when the rate law involved by only one concentration term.

t(1/2)  ∞ a1-n

t(1/2) = k’ 1/an-1

log t(1/2) = log k’ + (1-n)a

Graph of logt1/2 vs log a, gives a straight line with slope (1-n) , where 'n' is the order of the reaction.

Determining the slope we can find the order n.

If half life at different concentrations is given then.

(t_{1/2})_1} \alpha \frac{1}{a_{1}^{n-1}}

and

(t_{1/2})_2} \alpha \frac{1}{a_{2}^{n-1}}

\therefore \frac{(t_{1/2})_1}{(t_{1/2})_2} =(\frac{a_2}{a_1})^{n-1}

Taking logarithm and rearranging

n=1+\frac{log(t_{1/2})-log(t_{1/2})_2}{loga_2 -loga_1}

Plots of half-lives concentration (t1/2  ∞  a1-a):

plots-of-half-lives-concentration

This relation can be used to determine order of reaction 'n'  

 

Van't Hoff Differential Method

As we know that, the rate of a reaction varies as the nth power of the concentration of the reactant where 'n' is the order of the reaction.

Thus, for two different initial concentrations C1 and C2, equations can be written in the form

log(\frac{dC_1}{dt})=logk+nlogC_{1} ….(i)

and

log(\frac{dC_2}{dt})=logk+nlogC_{2}....(ii)

Taking logarithms,

Subtracting Eq. (ii) from (i),

log(\frac{dC_1}{dt})- log(\frac{dC_2}{dt})=n(logC_1 - log C_2)

or  

n = [log(-(dC1)/dt)-log((dC2)/dt)] ÷ [logC1 - log C2]     ....(iii)

-dc1/dt and -dc2/dt are determined from concentration vs. time graphs and the value of 'n' can be determined.