rates and equilibrium

Question 1

collision theory

Answer 1

reactant particles must collide for chemical reaction to occur w/ correct orientation and sufficient energy

Question 2

define activation energy

Answer 2

the minimum amount of energy required for a reaction to take place

Question 3

effect of changing concentration on equilibrium

Answer 3

increasing conc of reactant or product will favour reaction where substance is reactant, so removing substance

if substance = removed, equil. will shift in order to replace it

adding or removing solids/liquids will X change equ = must cgange CONC

Question 4

describe la chatelier’s principle

Answer 4

a system in equilibrium has the tendency to partially oppose any disruption to re-establish equilibrium and minimise effects of changes

Question 5

define rate of reaction

Answer 5

the change in concentration of a reactant or product per unit time

Question 6

effect of using catalysts on RR

Answer 6

-reduce AE of reaction as reactant particles on catalyst surface disrupt bonds w/in molecule -> different chemical pathway
-increases proportions of particles w sufficient energy
-increase frequency of successful collision
-increase ROR

Question 7

effect of changing temp of reactants on ROR

Answer 7

-increase temp = increase kinetic energy of reactant particles
-increase proportion of particles w sufficient energy
-increase frequency of successful collisions
-increase ROR

Question 8

effect of changing pressure of reactant gases on ROR

Answer 8

-decrease volume = increase pressure
-increase volume = decrease pressure
-increase number of particles per unit volume if volume dec + pressure incr
-increase frequency of collision
-increase freq. of successful
-increase ROR

Question 9

effect of surface area of solid reactants on ROR

Answer 9

-increase surface area = increased no. of particles that are exposed and available for collision
-increase frequency of collisions
-increase frequency of successful collisions
-increase ROR

Question 10

effect of changing concentration of solution on ROR

Answer 10

-increase conc of solution
-increase no. of particles per unit volume
-increase frequency of collisions
-increase frequency of successful collisions

Question 11

terminology for equilibrium

Answer 11

forward reaction is favoured = equilibrium is shifted to the right
reverse reaction is favoured = equilibrium is shifted to the left

Question 12

what is dynamic equilibrium

Answer 12

-when the rate of the fwd reaction equals the rate of the rev reaction - both processes are occurring simultaneously
-no observable change
-concentration of products and reactants remain constant but x always equal

Question 13

is dynamic equilibrium a closed or open system?

Answer 13

closed system to prevent reactant or products from escaping or being introduced

Question 14

effect of changing pressure on equilibrium

Answer 14

increase pressure = always favours reaction that produces fewer moles of gas

decrease pressure = favours reaction that produces more moles of gas

Question 15

effect of changing temp on equilibrium

Answer 15

increase temp = favour endothermic reaction, where enthalpy change = POS

decrease temp = favour exothermic reaction, where enthalpy change = NEG

Question 16

effect of adding catalyst on equilibrium

Answer 16

increase rate of both forward and reverse reactions - equilibrium may be reached more quickly, but not favour one or change position of equilibrium

Question 17

define haber process

Answer 17

the industrial process of the manufacture of ammonia from hydrogen and nitrogen

Question 18

compromise positions of the haber process

Answer 18

-at 200 atm, lower pressure than preferred b/c higher pressure = increased energy costs + more exp. equip to maintain high pressure

-400-450 deg celcius, lower temp favours exo reaction but too slow of ROR and decrease eq. yield (maximise yield per day, not cycle)

-uses iron catalyst