Chemical Equilibrium Booklet

Question 1

what does a 0% yeild indicate

Answer 1

no apparent reaction has occurred and almost 100% of reactants are left

Question 2

what are 2 ways to describe the position of an equilibrium

Answer 2

percent yeild and equilibrium constant (Kc)

Question 3

what are the conditions necessary for a chemical reaction (3)

Answer 3

particles must collide; the reaction is reversible; rate of reaction depends on temperature, surface are and concentration

Question 4

whats the approximation rule

Answer 4

when the Concentration of the reactants divided by the Kc value is larger than 1000, you can disregard the change in concentration

Question 5

whats the percent yeild value in a quantitative/complete reaction

Answer 5

> 99.9%

Question 6

what does a <50% yeild indicate

Answer 6

reactants are favoured

Question 7

whats the percent yeild value in a reaction where products are favoured

Answer 7

> 50%

Question 8

whats the Kc value in a reaction where reactants are favoured

Answer 8

<1

Question 9

formula to calculate Kc of forward reaction

Answer 9

Kc(foward) = [products]/[reactants]

Question 10

whats the percent yeild value in a non-spontaneous reaction

Answer 10

0

Question 11

what does it mean if the Kc<1

Answer 11

the equilibrium favors reactants

Question 12

how is maximum concentration determined for a percent yeild calculation

Answer 12

using stoichiometry

Question 13

dynamic equilibrium

Answer 13

when opposing changes occur simultaneously at the same rate; equilibrium is always active

Question 14

what happens to the concentration of reactants as they react in a foward reaction and how does this affect the rate of the foward reaction

Answer 14

the concentration decreases which causes the reaction rate to decrease

Question 15

what are the steps for Kc calculations involving an ICE table

Answer 15

1). write out the equilibrium reaction and equilibrium law expression
2). draw an ICE chart
3). substitute given values
4). solve for unknown values (x)
5). solve for equilibrium concentrations and use those to determine Kc if needed

Question 16

what is percent yeild

Answer 16

yeild of a product measured at equilibrium compared with the maximum possible yeild of product

Question 17

what happens when Kc is 1

Answer 17

neither reactants or products are favored

Question 18

whats the Kc value in a reaction where products are favoured

Answer 18

> 1

Question 19

characteristics of an equilibrium constant value (6)

Answer 19

• depends on the systems temperature
• independent of the reagent concentrations
• not affected by catalyst’s
• not affected by time take to reach equilibrium
• normally stated as a numerical value ignoring any units
• the value is greater the more the system favors the formation of products

Question 20

what states of chemicals can not be included in a Kc expression and why

Answer 20

solids and liquids because the are assumed to have fixed concentrations

Question 21

what does a >99.9% percent yeild indicate

Answer 21

quantitative/complete reaction has occurred and there is almost no reactants left

Question 22

whats another name for a Kc expression

Answer 22

equilibrium law expression

Question 23

how do you use the equilibrium law expression to determine whether a system is at equilibrium

Answer 23

substitute in the given concentrations to the expression:
- if the value is equal to the given equilibrium constant, the system is at equilibrium
- if the value is larger, there are more products than reactants so the reaction must proceed to the left to reach equilibrium
- if the value is smaller, there are more reactants than products so the reaction must proceed to the right to reach equilibrium

Question 24

what do you assume about starting product concentrations if they are not given to you

Answer 24

that they equal 0

Question 25

static equilibrium

Answer 25

when the reaction has completely stopped and there is no movement between the reactants and products within the given reaction

Question 26

what do you bases your equilibrium law expression/ Kc expression on

Answer 26

based on a balanced equation written in net ionic form ignoring concentrations of pure solid or liquid phases

Question 27

what does it mean when ‘reactants are favored’

Answer 27

more reactants are present then products

Question 28

formula to calculate Kc of reverse reaction

Answer 28

Kc(reverse) = 1/Kc(foward) OR Kc(reverse) = [reactants]/[products]

Question 29

what happens to the concentration of products in a foward reaction and how does this affect the rate of the forward reaction

Answer 29

the concentration increases which causes the reaction rate to increase

Question 30

what does Kc mean

Answer 30

equilibrium constant

Question 31

what states of chemicals are included in a Kc expression

Answer 31

(g) and (aq)

Question 32

formula for percent yeild

Answer 32

% yeild = (equilibrium concentration)/(maximum concentration)

Question 33

whats the formula for Kc

Answer 33

Kc = ([product1]^mols of product1 x [product2]^mols of product2) / ([reactant1]^mols of reactant1 x [reactant2]^mols of reactant2)

Question 34

how do you get the Kc value to describe a reverse reaction

Answer 34

use a reciprocal fraction where the formula either becomes 1/(Kc of forward reaction) or (concentration of the reactants)/(concentration of the products)

Question 35

how is equilibrium concentration determined for a percent yeild calculation

Answer 35

experimentally

Question 36

whats the percent yeild value in a reaction where reactants are favoured

Answer 36

<50%

Question 37

what does a >50% yeild indicte`

Answer 37

products are favoured

Question 38

how do you determine Kc

Answer 38

concentration of the products/concentration of the reactants

Question 39

what does it mean if the Kc>1

Answer 39

the equilibrium favors products

Question 40

what does it mean when ‘products are favored’

Answer 40

more products are present than reactants

Question 41

what are the 4 conditions of a dynamic equilibrium

Answer 41

• the reaction has to be reversible so that the rates of the forward and reverse reactions can eventually become equal
• all observable (macroscopic) properties appear constant
• can only be achieved in a closed system
• the equilibrium can be approached from either direction so that it doesnt matter where you start in the reaction as the end result will always be the same