A.) Determine the rate law for the following reaction and...

a.) Determine the rate law for the following reaction and calculate the value of the rate constant (with units). A + B ? AB Experiment [A]0 (M) [B]0 (M) Initial Rate (M/s) 1 0.400 0.100 22.5 2 1.20 0.100 67.5 3 1.20 0.200 270 b.) Determine how much reactant would remain after 2.00 minutes if the reaction started with an initial concentration of A equal to 2.50 M. 2 A ? A2 rate = 6.50 × 10-3 s-1[A]

Transcript

00:01 Hello students, we have a question on chemical kinetics.

00:03 We can see that if we look at second and third reading we can see that if we keep the concentration of a constant and if we multiply the concentration of b by 2 the rate gets multiplied four times.

00:21 So, we can say that rate of reaction is proportional to b square.

00:29 Hence, the reaction will be of second order with respect to b.

00:34 Now, we can also see that keeping the concentration of b as constant and multiplying the concentration of a naught three times the rate will also get multiplied three times.

00:48 Hence, the rate is proportional to a naught to the power one.

00:53 So, reaction is of first order with respect to reactant a.

00:58 Hence, the rate all over will be equal to k3.

01:02 That means reaction will be of third order a b square.

01:08 This will be the correct rate law expression.

01:11 Now, let's calculate the rate constant.

01:14 From the first reading we can see that the rate of reaction is 22 .5 molar per second.

01:21 Let's consider k3 as k3 itself.

01:25 Concentration of a at this point is 0 .4 and concentration of b at this point is 0 .1.

01:34 This will be squared.

01:36 Now, from here we can calculate the value of k3.

01:41 Hence, finally, after calculation k3 will be equal to 5 .6 multiplied by 10 raised to the power 3 and since this is the third order reaction its units will be mole minus two liter square second inverse.

02:01 Now, let's move to the second question.

02:03 In the second question, we have been told that initial concentration of a reactant a is 2 .50 molar and rate constant of this first order reaction is 6 .5 multiplied by 10 raised to the power minus 3 per second.

02:21 Now, we have to calculate the concentration of a remaining after two minutes.

02:27 So, time is two minutes or we can say 120 seconds...

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