Chemistry - Ch. 18.1 and 18.3

Question 1

rate

Answer 1

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

Question 2

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

Answer 2

change in amount of reactant or product per unit of time

Question 3

What is the collision theory used for?

Answer 3

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

Question 4

Collision Theory

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

Answer 4

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.

Question 5

Activation Energy

Answer 5

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

Question 6

Activated Complex

Answer 6

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

Question 7

What is the lifetime of an activated complex?

When does it’s existence end?

What is it sometimes called?

(3)

Answer 7

10^(-13) seconds

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

The transition state

Question 8

Endothermic

Exothermic

Answer 8

absorbs heat

releases heat

Question 9

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

Answer 9

Temperature

Concentration

Particle Size

Use of a catalyst

Question 10

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

Answer 10

Increase Temp = Speeds up reaction, particles move faster

Decrease Temp = Slows down reaction, particles move slower

Question 11

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

Answer 11

Increase Concentration = Faster reaction rate, increases frequency of collision

Question 12

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

Answer 12

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

Question 13

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

Answer 13

Dissolve them

Grind into a fine powder

Question 14

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

Answer 14

Use a catalyst

Question 15

Catalyst

Answer 15

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

Question 16

What are enzymes?

Answer 16

the catalysts that increases the rates of biological reactions

Question 17

inhibitor

what does it do?

what happens to the reaction?

Answer 17

substance that interferes with the action of a catalyst

reduces the amount of catalyst available for a reaction

slows down or even stops.

Question 18

reversible reaction

Answer 18

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

Question 19

equilibrium position

what does this tell you?

Answer 19

the relative concentrations of the reactants and products at equilibrium

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

Question 20

Le Chatelier’s Principle

Answer 20

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

Question 21

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

Answer 21

Changes in the concentration of reactants or products

Changes in temps

Changes in pressure (gases only)

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

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

3

Answer 24

• 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

Question 25

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

Answer 25

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

Question 26

What is the value of a large Keq?

What does it mainly consist of?

(2)

Answer 26

3.1 x 10^11

Product

Question 27

What is the value of a small Keq?

What does it mainly consist of?

(2)

Answer 27

3.1 x 10^-11

Reactant

Question 28

What is the value of an intermediate Keq?

What does it mainly consist of?

(2)

Answer 28

0.15 or 50

The mixture will have significant amounts of both reactant and product

Question 29

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

Answer 29

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