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Chemistry 18.1. Rates of Reaction. 18.1. - PowerPoint PPT Presentation

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Page 1: Chemistry 18.1

Slide 1 of 25

Chemistry 18.1

Page 2: Chemistry 18.1

© Copyright Pearson Prentice Hall

Slide 2 of 25

Rates of Reaction

The heat given off by the corrosion reaction of an iron-magnesium alloy with salt water can produce a hot meal. The rate of reaction is increased by adding salt water, so heat is produced rapidly. You will learn some ways in which the rate of a reaction can be increased.

18.1

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© Copyright Pearson Prentice Hall

Rates of Reaction >

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Collision Theory

Collision Theory

How is the rate of a chemical change expressed?

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Rates of Reaction >

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18.1 Collision Theory

In chemistry, the rate of chemical change, or the reaction rate, is usually expressed as the amount of reactant changing per unit time.

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© Copyright Pearson Prentice Hall

>Rates of Reaction18.1 Collision Theory

A rate is a measure of the speed of any change that occurs within an interval of time.

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© Copyright Pearson Prentice Hall

>Rates of Reaction

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Collision Theory

Rates of chemical reactions are often measured as a change in the number of moles during an interval of time.

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© Copyright Pearson Prentice Hall

>Rates of Reaction Collision Theory

According to collision theory, atoms, ions, and molecules can react to form products when they collide with one another, provided that the colliding particles have enough kinetic energy.

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>Rates of Reaction

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Collision Theory

Effective Collision

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© Copyright Pearson Prentice Hall

>Rates of Reaction

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Collision Theory

Ineffective Collision

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>Rates of Reaction Collision Theory

The minimum energy that colliding particles must have in order to react is called the activation energy.

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>Rates of Reaction Collision Theory

An activated complex is an unstable arrangement of atoms that forms momentarily at the peak of the activation-energy barrier.

The activated complex is sometimes called the transition state.

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Rates of Reaction >

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Factors Affecting Reaction Rates

Factors Affecting Reaction Rates

What four factors influence the rate of a chemical reaction?

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© Copyright Pearson Prentice Hall

Rates of Reaction >

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Factors Affecting Reaction Rates

The rate of a chemical reaction depends upon temperature, concentration, particle size, and the use of a catalyst.

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© Copyright Pearson Prentice Hall

Rates of Reaction >

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Factors Affecting Reaction Rates

Animation 22

Explore several factors that control the speed of a reaction.

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© Copyright Pearson Prentice Hall

>Rates of Reaction Factors Affecting Reaction Rates

Temperature

Storing foods in a refrigerator keeps them fresh longer. Low temperatures slow microbial action.

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© Copyright Pearson Prentice Hall

>Rates of Reaction Factors Affecting Reaction Rates

Concentration

a. In air, a lighted splint glows and soon goes out.

b. When placed in pure oxygen (higher oxygen concentration), the splint bursts into flame.

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>Rates of Reaction Factors Affecting Reaction Rates

Particle Size

The minute size of the reactant particles (grain dust), and the mixture of the grain dust with oxygen in the air caused the reaction to be explosive, destroying the grain elevator.

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© Copyright Pearson Prentice Hall

>Rates of Reaction Factors Affecting Reaction Rates

Catalysts

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Rates of Reaction >

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Factors Affecting Reaction Rates

Simulation 23

Explore the effects of concentration, temperature, and a catalyst on reaction rate.

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>Rates of Reaction Factors Affecting Reaction Rates

An inhibitor is a substance that interferes with the action of a catalyst. Antioxidants and antimicrobials used in drying fruits and preserving fruit juices slow the action of microbes and limit contact with air.

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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

18.1 Section Quiz.

18.1.

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18.1 Section Quiz.

1. The units below that would be appropriate to measure the rate of a chemical reaction is

a. mmol/s.

b. mol/L.

c. kJ/mol.

d. h/mol.

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18.1 Section Quiz.

2. In a chemical reaction, the energy of reactants is always

a. greater than the energy of the products.

b. more than the activation energy.

c. less than the activation energy.

d. less than the energy of the products.

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© Copyright Pearson Prentice Hall

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18.1 Section Quiz.

3. An increase in which one of the following will NOT increase the reaction rate?

a. temperature

b. concentration of reactants

c. total mass of reactants

d. surface area of reactants

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© Copyright Pearson Prentice Hall

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18.1 Section Quiz.

4. A catalyst works because it

a. lowers the activation energy.

b. increases the temperature.

c. is permanently changed in a reaction.

d. supplies energy to a reaction.

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