chemical equilibrium Flashcards
what reactions are we looking at?
- reversible reactions
- never fully complete because of dynamic nature
- called equilibrium chemical reactions
what do equilibrium chemical reactions entail?
- two reactions (forward and back) occurring at the same time
what is equilibrium?
the rate of the reactions thus if a reaction system is at equilibrium, the rate of both reactions is equal
what is the equilibrium constant and what is its unit?
Kc
M
what is Kc?
a study of yield
what is the equation of the equilibrium constant?
[product]/[reactant]
coefficients are represented as powers
what does a large and small Kc represent?
- large: large [products]
- low: low [products]
what value must Kc be to be at =m?
between 10^-4 and 10^4
Kc bigger than 10^4?
favours a forward reaction, large yield
Kc smaller than 10^-4
favours a backwards reaction, low yield
how do you find M?
use index laws within the fraction to solve
how do you calculate concentration?
c = n/V
how do you solve the concentration of a chemical;?
sub and rearrange
what is the RICE method?
- 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
double stoichiometry?
square Kc
halve stoichiometry?
square root Kc
reverse reaction?
inverse Kc
what are the two classifications of equilibrium systems?
open system: matter and energy can interact with surroundings eg. bushfire
closed system: matter and energy are only exchanged within the system. eg. submarines
does exo or endo affect =M?
yes, in a closed system
how can energy be written in reactions? exo? endo?
as product in exo and a reactant in endo
what conditions change Kc?
temperature only
what is the definition of LCP?
if a system is subjected to a change, the =m system adjusts itself to partially oppose the change, re-establishing the =m.
how is LCP used in industry?
changes are Mae to increase yield (amount of reactant made into product)
how is LCP used in physiological perspectives?
- maintaining of homeostasis (=m)
how can =m systems be analysed?
- Kc values
- experimental ‘colour’ observations
how can concentration of reactants affect the =m in LCP?
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
how can concentration of products affect =m in LCP?
increase concentration: add a few drops of product. backwards
decrease: remove product. forwards
how do you change pressure in an aqueous environment?
- dilute by adding more solvent (usually h2O)
- concentrate by removing solvent (evaporate)
how do you change pressure in a gaseous environment?
- change size or volume of reaction system eg. syringe
how does pressure affect reactions according to LCP?
- 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
how does a catalyst affect reactions LCP?
speeds up forward and back reaction so =m is reached in shorter time
how does temperature affect in endo?
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
how does temperature affect in exo?
increase: back reaction, decreased Kc
decrease: forward reaction, increase Kc
what is temperature the biggest factor in?
yeild
what are LCP considerations?
- 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
what do concentration v time graphs show?
- the change induced on the system
- the response of that system to oppose the change
how does an increase of product look on a graph?
- 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
how does volume change look on a graph?
a sharp increase/decrease in all reactants and products
how does a temp change look on a graph?
a gradual increase/decrease
describe competing equilibria: carbon monoxide poisoning
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
describe osteoporosis?
- don’t get enough Ca2+ so bone dissociates
describe ocean chemistry
increased carbon dioxide, produced increased ocean acidity through a series of reactions
describe ventilation
hypoventilation: breathing at low rate there fore not releasing a lot of CO2
hyperventilation: breathing rate is increased therefore releasing lots of CO2
