Describe at least two experiments you could perform to determine a rate law.

Name: Problem 2, Chapter 12: Chemistry
Uploaded: 2019-08-11T06:13:34-08:00
Duration: 16 min 55 s
Channel: Ibrahim Abdullahi
Description: Describe at least two experiments you could perform to determine a rate law.

Describe at least two experiments you could perform to...

Key Concepts

Method of Initial Rates

This concept involves measuring the initial rate of a reaction under different starting concentrations of the reactants. By comparing how the initial rate changes as each reactant concentration is varied while keeping the others constant, one can determine the order of the reaction with respect to each reactant and, subsequently, the overall rate law.

Integrated Rate Law Analysis

This approach focuses on monitoring the concentration of a reactant or product over time and fitting the data to various integrated rate laws (e.g., zero-order, first-order, or second-order forms). By plotting the appropriate functions of concentration versus time, the reaction order can be identified based on which plot yields a linear relation, thereby determining the rate law.

Transcript

00:01 Hi guys.

00:03 So today we're going to talk about problem to the problem acts us to explain the experiments we can use to determine a rate law.

00:15 So before we go into the details of the experiment, i think it's a good idea to explain what rate law is and we can build up from that.

00:30 So rate law is basically chemical reaction expression that shows how the rate of the reaction depends on the concentration of the reactants i'll give an example when you have a nitrogen dioxide gas decomposing into nitric oxide and oxygen is it balanced no to its balance now.

01:22 Yeah.

01:23 So when you have this chemical reaction, you can actually write the rate law as negative k, the reactant and power of n, where this k is the rate constant and n is the order of the reaction, or you can see order of the reaction, which could be an integer or even fraction sometimes.

02:18 And quimbat to rate, rate is the change in concentration of the reactant or product with time, change in concentration with time.

02:38 So if the rate is expressed in terms of the reactant, it's usually expressed as negative because the reactants are consumed in the reaction.

02:56 On the other hand, if it's expressed in terms of the products, it's expressed as positive because products are formed and they accumulate over time.

03:12 So it's positive.

03:14 So when you take the change, it's positive.

03:20 So that's that about that.

03:22 So with the experiments, you can actually determine the value of k and n.

03:37 Yes, you cannot guess the values.

03:39 You have to actually determine them experimentally, and that is what the experiment does.

03:46 And when you get those values, the n and k, you plug them back into the rate equation and that will be the rate law.

04:04 So let's start with the first experiment.

04:08 The first experiment is derived from what we call the differential rate law.

04:19 And it's called the method of initial rate.

04:29 So the way this works is that the initial rate is determined, which is the instantaneous rate, the rate of reaction just after t equals zero.

04:50 So that rate is determined, and several experiments using different initial concentrations are carried out.

04:58 And the initial rate is determined for each run.

05:02 This allows us to determine the form of the law of the reaction...

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