1 / 30

# Rates of Reaction and Equilibrium - PowerPoint PPT Presentation

Rates of Reaction and Equilibrium . Rates of reaction = kinetics Equilibrium = balance . To react, atoms must get together: . Called the collision theory: Students act a chemical reaction 1. 2. 3. . To react, atoms must: . 1. Get together (collide)

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about ' Rates of Reaction and Equilibrium ' - greta

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

• Rates of reaction = kinetics

• Equilibrium = balance

• Called the collision theory:

• Students act a chemical reaction

• 1.

• 2.

• 3.

1. Get together (collide)

2. Get together in the right way (orientation)

Collide with the “correct” side of a molecule

NO₂ + CO ↦ NO + CO₂

Carbon must hit the O side of NO₂ to get one of the O from the NO.

3. Get together with enough energy (force) so that the electrons can be shared/transferred

• Activation energy (low or high)

Reaction rate of a chemical reaction:

measured by change in concentration per unit time

• Rate that reactants turn into products

• Measured by change in concentration (of reactants or products)

5 FACTORS AFFECTING REACTION RATES

3 factors relate to energy

2 factors relate to the particles

• Chemical reactions happen when atoms and compounds collide with each other

• Collide with sufficient force to break bonds

• Collide in the right position (orientation)

Energy

Characteristics

Concentration

Surface area

• Temperature

• Agitation

• Catalysts

• 1. temperature: increases temp INCREASES reaction rates

Why? *particles move faster and collide with greater intensity

2. agitation: increases reaction rate

Why? *increases likelihood of particles being exposed to one another; increase in collisions

examples: shaking, stirring

3. catalysts: substance that increases the reaction rate without being used up in the reaction.

Why? * lowers the ACTIVATION energy;

sort of “invites” reacting particles together so they will react

• concentration: increasing concentration of reactants increases rate

Why? *increasing # particles increases chance of collision resulting in a reaction

• 2. surface area: increasing will cause reaction rate to increase

Why? *greater exposure of reacting particles to each other

examples: pulverizing, crushing, chopping up, etc

Example: Logs vs. twigs

• Speed up the rate of reaction

### Chemical Equilibrium = Balance

Chemical EquilibriumKey Terms

• Reversible reactions

• Balance

• Impacted by concentration, temperature and pressure

• Closed system (no new reactants added, no product is removed)

• Equilibrium constant

• Keq = [products]

[reactants]

• Reversible reactions: ↔⇄

• Explain what a reversible reaction will do to products and reactants

• Reversible reactions: ↔⇄

• Often happens naturally

• Products can be turned back to reactants

• In other words:

Products recombine to form the original substances .

• Equilibrium = balance between the amount of reactants and products in a reversible reaction

Needs a closed system: no additional reactants added and no products are taken away or escape as a gas)

Dynamic equilibrium Forward and backward reactions taking place at the same rate

Achieving equilibrium: After a period of time, the concentrations of reactants and products will stabilize

Le Chatelier Principle

• If you change the conditions, the position of the equilibrium will shift to oppose the change.

• Apply stress

Upsetting the equilibrium = shifting the equilibrium

• Change temperature

If an endothermic reaction -absorb or release heat?

-example of types of reaction?

CaCO₃ + heat ⇄ CaO + CO₂

Add more heat (raise the temperature) to make more product

If an exothermic reaction– reduce the amount heat (lower the temperature) to make more product

Reaction will try to replace the heat that was taken away

• Change the pressure

• Important when gases react

• Many reactions will have greater volume on one side (more product or more reactant)

If we increase the pressure –

The reaction will “favor” the reaction side with less volume

If we lower the pressure –

The reaction will “favor” the reaction side with more volume

N₂ + 3 H₂ ⇄ 2NH₃

• TED Ed Lessons

• https://ed.ted.com/lessons/the-chemical-reaction-that-feeds-the-world-daniel-d-dulek

• New concept: equilibrium

Le Chatelier Principle

• If you change the conditions, the position of the equilibrium will shift to oppose the change.

• aA + bB⇆ cC + dD

• Keq= [C] [D]

[A] [B]

• Example: N₂ + 3 H₂ ⇄ 2NH₃

• Keq = [NH₃]²

[N₂] [H₂]³

Will use equilibrium constant when determining pH and pOH

Issues- Chemical reactions Good & Evil

• Haber received much criticism for his involvement in the development of chemical weapons in pre-World War II Germany, both from contemporaries and from modern-day scientists.

• The research results show the ambivalence of his scientific activity: on the one hand, development of ammonia synthesis for the manufacture of explosives and of a technical process for the industrial manufacture and use of poison gas in warfare; but on the other hand, development of an industrial process without which the food supply for today's world population would be greatly diminished

Review: Energy in chemical reactions

Exothermic chemical reaction

Review: Energy in chemical reactions

Endothermic chemical reaction