Chemistry - Ch. 18.1 and 18.3 Flashcards Preview

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Flashcards in Chemistry - Ch. 18.1 and 18.3 Deck (29):
1

rate

a measure of how much something changes within a specified amount of time

2

how is the rate of a chemical reaction (reaction rate) expressed?

change in amount of reactant or product per unit of time

3

What is the collision theory used for?

to relate the properties of particles to the rates of chemical reactions

4

Collision Theory

what happens if they don't have an effective collision?

particles can react to form products when they collide if the particles have enough kinetic energy

- an ineffective collision will result in the particles bouncing apart, unchanged.

5

Activation Energy

the minimum energy that colliding particles must have in order to react

6

Activated Complex

an unstable arrangement of atoms that forms for a moment at the peak of the activation-energy barrier

7

What is the lifetime of an activated complex?

When does it's existence end?

What is it sometimes called?

(3)

10^(-13) seconds

It's existence ends with the reformation of the reactants or the formation of products

The transition state

8

Endothermic

Exothermic

absorbs heat

releases heat

9

Factors that determine whether a molecular collision results in a reaction? (4)

Temperature

Concentration

Particle Size

Use of a catalyst

10

What effect does the temperature of a solid, liquid, or gas have on the rate of reaction?

Increase Temp = Speeds up reaction, particles move faster

Decrease Temp = Slows down reaction, particles move slower

11

What effect does the concentration of a solid, liquid, or gas have on the rate of reaction?

Increase Concentration = Faster reaction rate, increases frequency of collision

12

What effect does the particle size of a solid, liquid, or gas have on the rate of reaction?

Increase particle size = Slower reaction rate, smaller surface area, and a decrease in frequency of collisions

Decrease particle size = faster reaction rate, greater surface area, increase in frequency of collisions

13

What are two other ways to increase the surface area of a solid?

Dissolve them

Grind into a fine powder

14

What is the best way to increase the rate of reaction?

Use a catalyst

15

Catalyst

a substance that increases the rate of reaction without being used up during the reaction

16

What are enzymes?

the catalysts that increases the rates of biological reactions

17

inhibitor

what does it do?

what happens to the reaction?

substance that interferes with the action of a catalyst

reduces the amount of catalyst available for a reaction

slows down or even stops.

18

reversible reaction

one in which the conversion of reactants to products and the conversion of products to reactants occur at the same time

19

equilibrium position

what does this tell you?

the relative concentrations of the reactants and products at equilibrium

it tells you whether the forward or reverse reaction is more likely to happen

20

Le Chatelier's Principle

If a stress is applied to a system in dynamic equilibrium, the system changes in a way that relieves the stress

21

Stresses that upset the equilibrium of a chemical system? (3)

Changes in the concentration of reactants or products

Changes in temps

Changes in pressure (gases only)

22

effect of a change in concentration on a system at equilibrium?

Adding a product to a reaction at equilibrium pushes a reversible reaction in the direction of the reactants and vice-versa.

23

effect of a change in temperature on a system at equilibrium?

Increasing the temperature causes the equilibrium position of a reaction to shift in the direction that absorbs heat.

24

effect of a change in pressure on a system at equilibrium?

(3)

*Gases Only
* only occurs if there is an unequal number of moles of gas on each side of the equation - the side that has the least amount of moles is where the direction will shift towards

25

What does the size of an equilibrium constant indicate about a system at equilibrium?

The size of the equilibrium constant indicates whether reactants or products are more common at equilibrium.

26

What is the value of a large Keq?

What does it mainly consist of?

(2)

3.1 x 10^11

Product

27

What is the value of a small Keq?

What does it mainly consist of?

(2)

3.1 x 10^-11

Reactant

28

What is the value of an intermediate Keq?

What does it mainly consist of?

(2)

0.15 or 50

The mixture will have significant amounts of both reactant and product

29

What is the formula to find the equilibrium constant? (Keq)

Keq = [C]^c x [D]^d / [A]^a x [B]^b