1st order, 2nd order Rate reactions HELP

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Discussion Overview

The discussion revolves around understanding the concepts of first order, second order, and zero order rate reactions in chemical kinetics. Participants explore the definitions, relationships between reactant concentrations and reaction rates, and provide examples to clarify these concepts.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about the definitions and implications of reaction orders, indicating a lack of understanding despite reviewing their textbook.
  • Another participant suggests that the original poster's information is incomplete, implying that this may contribute to their confusion.
  • A participant explains that the order of a reaction reflects the relationship between the molarity of a reactant and its effect on the reaction rate.
  • Further clarification is provided on how the overall order of a reaction is calculated by summing the exponents in the rate law expression.
  • Specific examples are given to illustrate first and second order reactions, including a data set that demonstrates how to determine the order based on changes in concentration and reaction rate.
  • One participant derives a differential rate law from the provided data, concluding that the overall order of the reaction is three.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding reaction orders, with some providing clarifications while others remain confused. There is no consensus on the original poster's understanding, and multiple viewpoints on the definitions and implications of reaction orders are present.

Contextual Notes

Some assumptions about the definitions of reaction orders and the application of the rate law may not be fully articulated, leading to potential misunderstandings. The discussion includes specific mathematical relationships that may require further elaboration for clarity.

brandon1
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1st order, 2nd order Rate reactions HELP!

I have read the section of my book over and over and studied the practice problems, but I still do not understand 1st order, 2nd order, or 0 order rate reactions. What does it mean to be of any particular order?
 
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what are you talking about?

what lesson are you reading?

you information is incomplete, I'm sorry... that's why i cannot understand the order that you're referring to...
 
the order is just the relationship between the molarity of a reactant and the amount that it affects the rate of the reaction.
 
oh! so that's what brandon meant... lol! i didn't get it first...
 
If the rate of a reaction is given by :

[tex]rate= dP/dt = k*[A]^a \cdot <b>^b \cdot [C]^c \dots </b>[/tex]

then the order of the reaction is said to be a+b+c+...

So, a first order reaction has a rate that is linearly proportional to the concentration of one of the reactants. A second order reaction can be one of the two following kinds :

[tex]rate = k*[A]^2[/tex]
or
[tex]rate = k*[A][/tex]

A zero order reaction has a rate that is independent of the concentration of any of the reactants.
 
Let's say you have the following data:

A + B ---> C

[A]-----------reaction rate
.010----.020-----.050
.020----.020-----.100
.020----.040-----.400

Look at the first and second lines; [A] increases by a factor of 2 as does the reaction rate ( is held constant). 2^x = 2? x = 1, so [A] is a first order reactant. Now look at lines 2 and 3; [A] is held constant, increases by a factor of 2, and the reaction rate increases by a factor of 4. 2^x = 4? x = 2, so is a second order reactant.

Now you right the differential rate law like this: rate = k[A]^2. The overall order of the reaction is 3.
 

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