Chemical Equilibrium Booklet

Question 1

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

Answer 1

<50%

Question 2

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

Answer 2

> 50%

Question 3

whats the Kc value in a reaction where reactants are favoured

Answer 3

<1

Question 4

whats the Kc value in a reaction where products are favoured

Answer 4

> 1

Question 5

whats the percent yeild value in a non-spontaneous reaction

Answer 5

0

Question 6

whats the percent yeild value in a quantitative/complete reaction

Answer 6

> 99.9%

Question 7

what happens when Kc is 1

Answer 7

neither reactants or products are favored

Question 8

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

Answer 8

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

Question 9

dynamic equilibrium

Answer 9

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

Question 10

static equilibrium

Answer 10

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

Question 11

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 11

the concentration decreases which cases the reaction rate to decrease

Question 12

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

Answer 12

the concentration increases which causes the reaction rate to increase

Question 13

what are the 4 conditions of a dynamic equilibrium

Answer 13

• 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

Question 14

what is percent yeild

Answer 14

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

Question 15

formula for percent yeild

Answer 15

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

Question 16

how is equilibrium concentration determined for a percent yeild calculation

Answer 16

experimentally

Question 17

how is maximum concentration determined for a percent yeild calculation

Answer 17

using stoichiometry

Question 18

what does a <50% yeild indicate

Answer 18

reactants are favoured

Question 19

what does a >50% yeild indicte`

Answer 19

products are favoured

Question 20

what does a >99.9% percent yeild indicate

Answer 20

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

Question 21

what does a 0% yeild indicate

Answer 21

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

Question 22

what are 2 ways to describe the position of an equilibrium

Answer 22

percent yeild and equilibrium constant (Kc)

Question 23

what does Kc mean

Answer 23

equilibrium constant

Question 24

what does it mean if the Kc>1

Answer 24

the equilibrium favors products

Question 25

what does it mean if the Kc<1

Answer 25

the equilibrium favors reactants

Question 26

how do you determine Kc

Answer 26

concentration of the products/concentration of the reactants

Question 27

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

Answer 27

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

Question 28

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

Answer 28

solids and liquids because the are assumed to have fixed concentrations

Question 29

what do you write an equilibrium law expression/a Kc expression

Answer 29

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

Question 30

what states of chemicals are included in a Kc expression

Answer 30

(g) and (aq)

Question 31

whats another name for a Kc expression

Answer 31

equilibrium law expression

Question 32

characteristics of an equilibrium constant value (6)

Answer 32

• 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 33

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

Answer 33

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 34

what does it mean when ‘reactants are favored’

Answer 34

more reactants are present then products

Question 35

what does it mean when ‘products are favored’

Answer 35

more products are present than reactants

Question 36

what are the steps for Kc calculations involving an ICE table

Answer 36

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 37

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

Answer 37

that they equal 0