chemical equilibrium

Question 1

what reactions are we looking at?

Answer 1

• reversible reactions
• never fully complete because of dynamic nature
• called equilibrium chemical reactions

Question 2

what do equilibrium chemical reactions entail?

Answer 2

• two reactions (forward and back) occurring at the same time

Question 3

what is equilibrium?

Answer 3

the rate of the reactions thus if a reaction system is at equilibrium, the rate of both reactions is equal

Question 4

what is the equilibrium constant and what is its unit?

Answer 4

Kc

M

Question 5

what is Kc?

Answer 5

a study of yield

Question 6

what is the equation of the equilibrium constant?

Answer 6

[product]/[reactant]

coefficients are represented as powers

Question 7

what does a large and small Kc represent?

Answer 7

• large: large [products]

- low: low [products]

Question 8

what value must Kc be to be at =m?

Answer 8

between 10^-4 and 10^4

Question 9

Kc bigger than 10^4?

Answer 9

favours a forward reaction, large yield

Question 10

Kc smaller than 10^-4

Answer 10

favours a backwards reaction, low yield

Question 11

how do you find M?

Answer 11

use index laws within the fraction to solve

Question 12

how do you calculate concentration?

Answer 12

c = n/V

Question 13

how do you solve the concentration of a chemical;?

Answer 13

sub and rearrange

Question 14

what is the RICE method?

Answer 14

• write out ratios of stoich
• write out initial mol from question (some might be 0 if not specified)
• use on to see how much change there is in mol at =m
• use that mole amount and divide accordingly to match stocih and use that to subtract from initial amounts
• calculate cocentration from =m mol
• use that to calculate Kc

Question 15

double stoichiometry?

Answer 15

square Kc

Question 16

halve stoichiometry?

Answer 16

square root Kc

Question 17

reverse reaction?

Answer 17

inverse Kc

Question 18

what are the two classifications of equilibrium systems?

Answer 18

open system: matter and energy can interact with surroundings eg. bushfire
closed system: matter and energy are only exchanged within the system. eg. submarines

Question 19

does exo or endo affect =M?

Answer 19

yes, in a closed system

Question 20

how can energy be written in reactions? exo? endo?

Answer 20

as product in exo and a reactant in endo

Question 21

what conditions change Kc?

Answer 21

temperature only

Question 22

what is the definition of LCP?

Answer 22

if a system is subjected to a change, the =m system adjusts itself to partially oppose the change, re-establishing the =m.

Question 23

how is LCP used in industry?

Answer 23

changes are Mae to increase yield (amount of reactant made into product)

Question 24

how is LCP used in physiological perspectives?

Answer 24

• maintaining of homeostasis (=m)

Question 25

how can =m systems be analysed?

Answer 25

- Kc values | - experimental 'colour' observations

Question 26

how can concentration of reactants affect the =m in LCP?

Answer 26

addition: add a few drops, according to LCP the =m will favour a forward direction to re-establish =m decrease: add a chemical that is involved in a side reaction with a reactant. According to LCP, a backwards reaction will occur

Question 27

how can concentration of products affect =m in LCP?

Answer 27

increase concentration: add a few drops of product. backwards decrease: remove product. forwards

Question 28

how do you change pressure in an aqueous environment?

Answer 28

- dilute by adding more solvent (usually h2O) | - concentrate by removing solvent (evaporate)

Question 29

how do you change pressure in a gaseous environment?

Answer 29

- change size or volume of reaction system eg. syringe

Question 30

how does pressure affect reactions according to LCP?

Answer 30

- increase of pressure (decrease volume) promotes a reaction towards side with fewer particles - decreased pressure (increased volume) promotes a reaction to the side with more particles

Question 31

how does a catalyst affect reactions LCP?

Answer 31

speeds up forward and back reaction so =m is reached in shorter time

Question 32

how does temperature affect in endo?

Answer 32

increase: increase in reactants therefore a forward reaction is promoted. This is a permanent forward reaction until the chemist decides. increases Kc decrease: decrease of reactants. back reaction. decrease of Kc

Question 33

how does temperature affect in exo?

Answer 33

increase: back reaction, decreased Kc decrease: forward reaction, increase Kc

Question 34

what is temperature the biggest factor in?

Answer 34

yeild

Question 35

what are LCP considerations?

Answer 35

- Kc is only affected by temp - volume/pressure: if stoich of reactants and products are equal, then there will be no change. Adding an inert gas causes a change to pressure but because they are not reactive, there is no change to =m system

Question 36

what do concentration v time graphs show?

Answer 36

- the change induced on the system | - the response of that system to oppose the change

Question 37

how does an increase of product look on a graph?

Answer 37

- increase that substance by the stoich and then decrease it nearly to normal - other reactants will gradually move down in conc. - products will increase - all according to stoich

Question 38

how does volume change look on a graph?

Answer 38

a sharp increase/decrease in all reactants and products

Question 39

how does a temp change look on a graph?

Answer 39

a gradual increase/decrease

Question 40

describe competing equilibria: carbon monoxide poisoning

Answer 40

Hb + O2 Hb-O2 CO has a greater affinity for Hb (20 000 times greater) than O2 and forms Hb-CO (carboxy Haemoglobin) symptoms: - Hb-O2 breaks down - no oxygen to cells - cellular respiration stops - death

Question 41

describe osteoporosis?

Answer 41

- don't get enough Ca2+ so bone dissociates

Question 42

describe ocean chemistry

Answer 42

increased carbon dioxide, produced increased ocean acidity through a series of reactions

Question 43

describe ventilation

Answer 43

hypoventilation: breathing at low rate there fore not releasing a lot of CO2 hyperventilation: breathing rate is increased therefore releasing lots of CO2