Unit 8A

Question 1

Rate

Answer 1

Change that occurs within an interval of time

Question 2

Reaction rate

Answer 2

The changing reactants to products (or the reverse) per unit of time

Question 3

Reversible reactions

Answer 3

A reaction that can move in both the forward and reverse directions
In a chemical equation, a double sided arrow is used to represent a reversible reaction in the balanced equation

Question 4

Forward reaction

Answer 4

When reactants convert to products

Question 5

Reverse reaction

Answer 5

When products reform reactants

Question 6

STUDY ENERGY DIAGRAMS P1 OF NOTES

Answer 6

Okay

Question 7

Activation energy

Answer 7

The minimum amount of energy required in order to get a reaction started (to get to the top of the hill)
Can be calculated for both forward and reverse reactions

Question 8

Activated complex/transition state

Answer 8

Can be found at the peak of the energy diagram. A temporary arrangement formed by the reactants, where they have enough energy to form products OR go in the reverse direction and reform reactants.

Question 9

Endothermic

Answer 9

Reactions that require an input of energy to occur ex photosynthesis

Question 10

Exothermic

Answer 10

Reactions that release energy ex combustion

Question 11

Enthalpy

Answer 11

Change in heat energy (products-reactants)

Question 12

Collision theory

Answer 12

For a reaction to occur it is necessary for the reacting species (atoms or molecules) to come together or collide with one another. Not all collisions, however, bring about chemical change.
To be effective, particles must collide with enough kinetic energy AND must collide in the proper orientation.

Question 13

Factors affecting reaction rates

Answer 13

Temperature, concentration, particle size, catalyst

Question 14

Temperature

Answer 14

Generally, an increase in temperature increases reaction rates, while a decrease slows a reaction down.
Increasing temp speeds up particles, increasing kinetic energy

Question 15

Concentration

Answer 15

In a given volume, the number of particles affects the rate of reaction. Increasing the number of particles increases the concentration and the reaction rate.
More particles will increase the reaction rate

Question 16

Particle size

Answer 16

The smaller the particles, the greater the surface area for a given mass of particles. An increase in surface area increases the rate of reaction.
With more exposed area to react, this increases the rate of reaction

Question 17

Catalyst

Answer 17

Any substance that increases the rate of a reaction without being consumed
Catalysts allow reactions to proceed by lowering the activation energy.
Ex human enzymes

Question 18

Chemical equilibrium

Answer 18

The state at which the forward and reverse reactions take place at the same rate

Question 19

Difference between rate and concentration

Answer 19

Although the rates of the forward and reverse reactions are equal at chemical equilibrium, the concentrations are not necessarily the same

Question 20

Favored

Answer 20

The thing with the higher concentration is favored

Question 21

Catalysts

Answer 21

Although catalysts speed up a reaction rate, they will not affect the concentration of reactants and products present at equilibrium
They simply decrease the time it takes to establish equilibrium

Question 22

Le Châtelier’s principle

Answer 22

When a stress is applied to a system at equilibrium, the equilibrium will shift in order to relieve stress

Question 23

Factors affecting equilibrium

Answer 23

Concentration, temperature, pressure/volume

Question 24

Concentration

Answer 24

Changing the amount, or concentration, of any reactant or product in a system at equilibrium disturbs the equilibrium
Adding a product shifts equilibrium to left, products will decrease, reactants increase
Adding reactant shifts to right, products increase, reactants decrease

Question 25

Temperature

Answer 25

Increasing the temperature causes the equilibrium position of a reaction to shift in the direction that will absorb heat
Adding heat shifts to left
Taking away heat shifts to right

Question 26

Pressure/volume

Answer 26

Changing pressure only affects an equilibrium with an uneven number of reactants and products (gas phase)
Increasing pressure will shift the equilibrium in the direction of the least amount of number of molecules of gas
Change in volume is a change in pressure
Reducing volume will increase pressure, and vice versa
Increasing pressure will shift equilibrium to side with less moles, vice versa

Question 27

Equilibrium constant expressions

Answer 27

Can be used to determine whether products or reactants are favored in a chemical equilibrium

Question 28

Steps for determining Keq

Answer 28

Cross off any reactants or products that are in the solid or liquid state
Write the product in the numerator, using brackets (which represent concentration) to separate them if there is more than one
Write the reactant in the denominator, using brackets if there is more than one
Raise each substance’s concentration to the power equal to the substance’s coefficient in the balanced chemical equation

Question 29

General Keq formula for aA + bB cC + dD

Answer 29

Keq = ((C)^c (D)^d)/((A)^a (B)^b)

Question 30

If Keq is very…
High
Low
Close to one

Answer 30

Products favored
Reactants favored
Roughly equal amounts of products and reactant present at equilibrium