rates & equilibrium

Question 1

collision theory

Answer 1

1. reactant particles must collide
2. reactant must collide with sufficient energy break bonds within reactant molecules
3. reactant particles must collide with the correct orientation to break bonds

Question 2

activation energy

Answer 2

minimum amount of energy needed for a reaction to occur

Question 3

rate of reaction

Answer 3

comparison of two measurements usually concentration/time (per unit time)

Question 4

affect of surface area on rate

Answer 4

increased SA = Increased frequency of successful collisions

Question 5

affect of concentration on rate

Answer 5

increased concentration = increased successful collisions

Question 6

affect of pressure of gas systems on rate

Answer 6

increased pressure = increased successful collisions
eg. by decreasing volume of a container

Question 7

affect temp on rate

Answer 7

puts energy into system (kinetic)
greater proportion of particles have sufficient energy
increases number of successful collisions
distribution shifts to right

Question 8

affect catalyst on rate

Answer 8

provide an alternative reaction pathway
lower activation energy
greater proportion of particles have sufficient energy
increased number of successful collisions
activation energy shifts left

Question 9

Equilibrium constant expression

Answer 9

[products]^/[reactants]^

Question 10

factor that can affect Kc

Answer 10

Temperature

Question 11

K is greater than 10^4

Answer 11

forward reaction / essentially completion

Question 12

K is less than 10^-4

Answer 12

reaction occurs to a negligible extent / back reaction

Question 13

K between 10^4 and 10^-4

Answer 13

forward and back reaction occur to a moderate extent

Question 14

K if equation is reversed, doubled or halved

Answer 14

reversed = 1/K
doubled/tripled = K^2 or K^3
halved = square root of K

Question 15

Temp effect on K

Answer 15

exothermic = temp increases = K decreases
endothermic = temp increases = K increases

Question 16

how system shifts when
K>Q
K

Answer 16

K>Q —- shifts right
K

Question 17

K increases
K decreases

Answer 17

forward reaction more favoured
back reaction more favoured

Question 18

le chatelier’s principle

Answer 18

if an equilibrium system is subjected to change, then the system will shift in a direction that partially opposes that change

Question 19

changes to an equilibrium system
- change in temp
- adding a catalyst
- adding an inert gas
- add reactant/remove product
-remove reactant/add product

Answer 19

• increases temp: exothermic-> shifts left; endothermic-> shifts right
• adding a catalyst: no change (rate of each reaction increases equally)
• adding an inert gas: no change
• add reactant/remove product: shifts right
• remove reactant/add product: shifts left

Question 20

size of relative gradients?
2NO2
N2O4

Answer 20

2NO2 has double as steep gradient as N2O4 because of the 2:1 mole ratio in the equation