rate, equilibrium and yield Flashcards
collision theory
particles must collide with correct orientation and sufficient energy in order to disrupt bonds in the molecule –> form a successful collision
maxwell boltzmann distribution
- demonstrates a range of energies of particles (kinetic)
-area under the curve is equal to the total number of particles in the sample - for reaction the particles must have enoigh energy to overcome activation energy.
activation energy
- Ea is minimum amount of energy required to generate a reaction
rate of reaction
- the speed at which a reaction occurs
- ror is measured by change in concentration of a reactant or product per unit time
factors affecting ROR
- SA, temp, concentration, pressure of gases, catalyst
how does SA influence ROR
- increasing the SA, increase frequency of fruitful / successful collisions bw particles will increase ROR
how does conc. influence ROR?
increasing concentration, increase successful collisions will increase ROR
how does pressure affect ROR?
increase frequency of successful collisions per unit time - done by decreasing the volumw of a container/vessel b/c decrease space for particles to collide
catalysts influencing ROR
-provides an alternate pathway by lowering activation energy for a particular reaction
- particles on the surface distort and disrupt the bonds w/in molecules hence lowers Ea required for reaction-> greater proportion of particles w energy greater than Ea and successful collisions - increase ROR
effect of temp on ROR
-increase proportion of particles with sufficient energy for a reaction - increase proportion of successful collisions
ways to measure ROR
to determine how fast a reaction occurs:
- measure rate of gas production
- measure change in mass
- for reaction w acids and bases - measure change in pH over time
- if produces a precipitate then measure time it takes for solution to become cloudy
extent of reaction
how far a chemical reaction proceeds
type of catalysts
- homogenous - same state as reactant+ product
-heterogenous - different state to reactants + products
equilibria - a closed system
-when forward and back reactions OCCUR at the same rate the reaction is at equilibrium
- occur in reversible reaction
key factors of equilibrium
- amount (mol and mass) of chemical substances are constant
- conc. of chem. substances are constant
-total gas pressure is constant
-temperature is constant
equilibrium law expression
K= (C)c x (D)d
—————
(A)a x (B)b
what is K a measure of
the extent of a reaction ,not ROR
what influences equilibrium constant (K)
- changes with temp
- not depend on initial conc. of substances
equilibrium constant - extent of reaction
. bw 10^-4 and 10^4 = significant
. > 10^4 = almost complete
. <10^-4 = negligible reaction
temperature and K
exothermic - temp. increase - K decreases
endothermic - temp increase - K increases
If K is less than Q
reaction shifts left
If K is greater than Q
reaction will shift right
If K is equal to Q
no shift in equilibrium
tackling equilibrium question - layout
I - intital
C - change
E - equilibrium
F - final conc
le chatelier’s principle
IF AN EQUILIBRIUM SYSTEM IS SUBJECTED TO A CHANGE, THEN THE SYSTEM WILL SHIFT IN A DIRECTION THAT PARTIALLY OPPOSES THAT CHANGE
changes an equilibrium system may be subjected to include:
- A change in temperature (shift depends upon the reaction being endothermic /exothermic)
-Adding a catalyst (nochange)
-Adding an inert gas (no change)
-Addition of a reactant or removal of product (will favour forward reaction)
-Removal of a reactant or addition of a product (will favour back reaction)
-A change in pressure
-Dilution(solutions)
catalyst effect on equilibrium
- NO EFFECT b/c catalyst will affect the forward and back reaction equally
adding an inert gas - effect on equilibrium
NO EFFECT - gas is unreactive so takes no part in the reaction
change to equilibrium - addition of reactant
- formation of more products - a net forward reaction - equilibrium shifts right
change to equilibrium - adding a product
- formation of more reactants - net reverse reaction - equilibrium will shift to left
change to equilibrium - remove product
- form more products - net forward reaction - equilibrium shifts right
effect of changing temp on equilibrium
increase temp = favour endothermic reaction, where enthalpy change = POS bc system wants to reduce temperature
decrease temp = favour exothermic reaction, where enthalpy change = NEG bc system wants to increase temp
effect of changing pressure on equilibrium
decrease pressure = favour fewer gas moles
increase pressure = favours more gas moles
what is the haber process
industrial manufacturing of NH3 from H and N
conditions of haber process
200 atm , 400-450 celcius and iron catalyst
% yield equation
actual yield / theoretical yield x 100
how to increase yield for haber process
decrease temp, increase pressure , excess of reactant or removal of a product in order to favour the forward reaction
health and safety considerations - haber process
pressurised system , dangerous if inhaled , toxic and corrosive
what to do when Kc is reversed
use the reciprical
what to do when Kc is halved
square root
effect of dilution on equilibrium
conc decrease for all particles, favour reaction that will produce the most mol.
on graph why does the curve never return to same point
SYSTEM CAN ONLY PARTIALLY OPPOSE CHANGE
CO poisoning
instead of oxygen binding to haemoglobin the carbon monoxide binds
- problem because CO has much higher K value and affinity to bind with Hb4
how to combat CO poisoning
must significantly increase conc of O2 to encourage Hb4 and O2 to react which will then cause back reaction of Hb4CO4 to attempt to increase Hb4 in system which then increase Hb4 to bind with O2
how can Kc be high at a temp but ROR is low
Kc does not indicate ROR
limiting reagant
can cause a reaction to cease - decrease ROR
faradays 1st law
the amount of any substance discharged at an electrode during electrolysis is directly proportional to the quantity of electric charge passed through - linear
- mass gained at cathode= mass lost at anode
faradays 2nd law
- the amount in mol. of any substance discharged at an electrode during electrolysis is the reciprocal of the charge of the charge on the ion
- greater charge on the ion then greater electrical charge to discharge ion
