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AP Chemistry 2.3 Chemical Reaction Rates 3 Views


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AP Chemistry 2.3 Chemical Reaction Rates. What is the experimental rate law for this reaction?

Language:
English Language

Transcript

00:03

And here’s your Shmoop du jour, brought to you by reaction rate.

00:07

Hey, think fast! …Ooh, that’s gotta hurt. [Boy strikes a ball with a bat and ball hits man in face]

00:10

Sorry…

00:11

Here’s today’s problem:

00:12

The reaction: A + B yields C was run three different times, and each time, the concentrations

00:18

of the reactants were altered.

00:20

The reaction rate was also measured each time the reaction was run, as shown in the table.

00:25

What is the experimental rate law for this reaction? [Table of experiment measurements]

00:28

And here are your potential answers.

00:31

To answer this question, we’ll need to examine the experimental data and deduce the appropriate

00:38

rate law for this reaction. [Doctor with a zombie-looking man on a table]

00:41

The reactants here are species A and B. In the three experiments shown in the table,

00:46

the initial concentrations of A and B are varied.

00:49

Because everyone is special in their own way. [Woman hugging a young boy]

00:51

Anyway, between experiments 1 and 3, the initial concentration of A is doubled while the initial

00:58

concentration of B stays the same.

01:00

We can use these two data points to find out how the rate depends on the concentration [Rate swinging and A grabs it]

01:04

of species A without worrying about species B.

01:06

So, what is the dependence on A? [A and B sitting on a couch]

01:09

When the initial concentration of A is doubled, the rate stays the same, so it doesn’t depend

01:14

on A at all.

01:15

Kind of like how your parents don’t depend on you to do the dishes anymore. [Girl sitting on a couch with a pizza]

01:18

Yeah, we know, you'd get to them "in a minute".

01:20

Whatever you say.

01:21

So between experiments 1 and 2, the initial concentration of B is doubled, while the initial

01:26

concentration of A stays the same.

01:28

With these two points, we can find how the rate depends on species B.

01:31

When the concentration of B is doubled, the rate increases by four times. [B increases in size and a hand holding 4 fingers appears]

01:36

That means the rate depends on B squared.

01:38

That's not quite like us… when our concentration is doubled, we make it through class without

01:42

falling asleep.

01:43

We know.

01:44

Not all heroes wear capes. [People staying awake in a classroom]

01:45

Anyway, now we know that the rate depends on the concentration of B squared, but it

01:50

doesn’t depend on A at all.

01:51

Looking at our answers, choice (A) fits the bill, as all the others include some dependence

01:56

on species A. So choice (A) is the right answer.

01:59

Now it’s time to get those dishes done. [A collection of dirty dishes]

02:03

Hey, where are you going?

02:05

Oh, brother.

02:06

Seriously, maybe your brother will do them instead. [Brother and sister run away]

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