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How Concentration and Temperature Affect Reaction Rates for Kids

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Gracey

21/06/2022

Chemistry

Rates of Reaction

How Concentration and Temperature Affect Reaction Rates for Kids

A comprehensive guide to reaction rates and kinetics, covering key concepts in physical chemistry. This summary explores how concentration affects reaction rate, understanding first and second order reactions, the rate determining step, and the Arrhenius equation.

  • Explains reaction rates and their dependence on concentration
  • Covers zero, first, and second-order reactions with their characteristics
  • Discusses concentration-time graphs and rate-concentration graphs
  • Introduces the concept of rate determining step and its importance
  • Explores the Arrhenius equation and its components
...

21/06/2022

467

Rates of Reaction
quantity reacted or produced
/ Time
rate=
rate= change in concentration
zero order the concentration of the reactant has n

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Rate-Concentration Graphs and Advanced Concepts

This page expands on rate-concentration graphs for different reaction orders and introduces more advanced concepts in chemical kinetics.

For zero-order reactions, the rate-concentration graph is a horizontal line, as the rate is constant regardless of concentration. The rate equation for a zero-order reaction is:

Example: rate = kAA⁰ = k

For first-order reactions, the rate-concentration graph is a straight line passing through the origin, with the gradient equal to the rate constant k. The rate equation for a first-order reaction is:

Example: rate = kAA¹

Second-order reactions have a more complex rate-concentration relationship, and the rate constant cannot be directly determined from the graph. The rate equation for a second-order reaction is:

Example: rate = kAA²

The page then introduces the concept of clock reactions, where the time from the start to a visual change is measured and assumed to represent the initial rate.

Definition: Rate Determining Step: The slowest step in a reaction mechanism, which determines the overall reaction rate.

The rate equation only includes reacting species involved in the rate-determining step.

The Arrhenius equation is introduced, relating reaction rate to temperature and activation energy:

Example: ln k = -Ea/RT + ln A

Where:

  • k is the rate constant
  • Ea is the activation energy
  • R is the gas constant
  • T is the temperature
  • A is the pre-exponential factor

Highlight: The Arrhenius equation takes into account the frequency of collisions with the correct orientation and represents the proportion of molecules that exceed the activation energy and have sufficient energy for a reaction to take place.

The page concludes by showing how to determine the activation energy from an Arrhenius plot, where the gradient is equal to -Ea/R.

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Chemistry

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21 Jun 2022

2 pages

How Concentration and Temperature Affect Reaction Rates for Kids

user profile picture

Gracey

@gracey_irtg

A comprehensive guide to reaction rates and kinetics, covering key concepts in physical chemistry. This summary explores how concentration affects reaction rate, understanding first and second order reactions, the rate determining step, and the Arrhenius equation.... Show more

Rates of Reaction
quantity reacted or produced
/ Time
rate=
rate= change in concentration
zero order the concentration of the reactant has n

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Rate-Concentration Graphs and Advanced Concepts

This page expands on rate-concentration graphs for different reaction orders and introduces more advanced concepts in chemical kinetics.

For zero-order reactions, the rate-concentration graph is a horizontal line, as the rate is constant regardless of concentration. The rate equation for a zero-order reaction is:

Example: rate = kAA⁰ = k

For first-order reactions, the rate-concentration graph is a straight line passing through the origin, with the gradient equal to the rate constant k. The rate equation for a first-order reaction is:

Example: rate = kAA¹

Second-order reactions have a more complex rate-concentration relationship, and the rate constant cannot be directly determined from the graph. The rate equation for a second-order reaction is:

Example: rate = kAA²

The page then introduces the concept of clock reactions, where the time from the start to a visual change is measured and assumed to represent the initial rate.

Definition: Rate Determining Step: The slowest step in a reaction mechanism, which determines the overall reaction rate.

The rate equation only includes reacting species involved in the rate-determining step.

The Arrhenius equation is introduced, relating reaction rate to temperature and activation energy:

Example: ln k = -Ea/RT + ln A

Where:

  • k is the rate constant
  • Ea is the activation energy
  • R is the gas constant
  • T is the temperature
  • A is the pre-exponential factor

Highlight: The Arrhenius equation takes into account the frequency of collisions with the correct orientation and represents the proportion of molecules that exceed the activation energy and have sufficient energy for a reaction to take place.

The page concludes by showing how to determine the activation energy from an Arrhenius plot, where the gradient is equal to -Ea/R.

Rates of Reaction
quantity reacted or produced
/ Time
rate=
rate= change in concentration
zero order the concentration of the reactant has n

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Rates of Reaction

This page introduces the concept of reaction rates and explores different reaction orders. It explains how concentration affects reaction rate for zero, first, and second-order reactions.

The rate of a reaction is defined as the quantity reacted or produced over time, or the change in concentration over time. The page then delves into the characteristics of different reaction orders:

Definition: Zero-order reaction: The concentration of the reactant has no effect on the rate.

Definition: First-order reaction: The rate depends on the reactant concentration to the power of 1. If the concentration doubles, the reaction rate increases by a factor of 2.

Definition: Second-order reaction: The rate depends on the concentration raised to the power of 2. If the concentration doubles, the reaction rate increases by a factor of 4.

The overall order of a reaction is the sum of the orders of each reactant. The page also introduces the concept of initial rate and provides concentration-time graphs for different reaction orders.

Highlight: For first-order reactions, the time for the concentration to halve halflifehalf-life is constant.

The rate constant for a first-order reaction can be calculated from the half-life using the equation:

Example: K = ln22 / t½

The page concludes with concentration-time graphs for zero, first, and second-order reactions, illustrating how the reaction rate changes over time for each order.

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