chapter 10

Question 1

what has to happen for a reaction to occur?

Answer 1

particles must collide with the correct orientation
energy of particles collision must be greater than activation energy

Question 2

how does a low concentration affect a reaction?

Answer 2

less particles in given volume
less frequent collisions
slower rate

Question 3

how does a high concentration affect a reaction?

Answer 3

more particles in a given volume
more frequent collisions
faster rate

Question 4

how does increasing the pressure affect a reaction?

Answer 4

only gases
gas molecules closer together
collide more frequently

Question 5

how can you measure a chemical reaction?

Answer 5

monitor removal of reactants
or
follow formation of a product

Question 6

what is a catalyst?

Answer 6

substance that increases rate of chemical reaction without being used up
provides an alternative reaction pathway with a lower activation energy

Question 7

what does the reaction graph of an endothermic reaction look like?

Answer 7

reactants below products

Question 8

what does the reaction graph of an exothermic reaction look like?

Answer 8

reactants above products

Question 9

what are homogeneous catalysts?

Answer 9

catalyst must have same physical state as reactant

Question 10

what are heterogeneous catalysts?

Answer 10

they have a different physical state to reactants

Question 11

what do heterogeneous catalysts do?

Answer 11

reactant molecule forms weak bonds with catalyst surface (adsorption)
bonds within reactant molecule break
new bonds form between different molecules
product molecules leave the catalyst surface (desorbed)

Question 12

how are catalysts sustainable?

Answer 12

lower temps needed for reactions to occur
less electricity needed from combustion of fossil fuels
reduction of co2 emissions etc

Question 13

what must a reaction have if it is in equilibrium?

Answer 13

system must remain closed
rate of forward reaction is equal to rate of reverse
concentration of reactions and products remain constant

Question 14

what is le chateliers principal?

Answer 14

when a system is in equilibrium, if subjected to external change, the system readjusts iyself to minimise effect of change

Question 15

what does increasing concentration do?

Answer 15

equilibrium will shift to the right

Question 16

what does increasing temperature do in exothermic reactions?

Answer 16

favours endothermic reaction
equilibrium shifts to the left

Question 16

what does increasing temperature do in endothermic reactions?

Answer 16

favours endothermic reaction
equilibrium shifts to the right

Question 17

what does increasing pressure do?

Answer 17

favours side with fewer moles

Question 18

what does a catalyst do in a reaction (equilibrium)?

Answer 18

does not change position of equilibrium
speed up rate of reaction
increase rate at which equilibrium is reached

Question 19

why does the curve not ever meet the y-axis (boltzmann distribution)?

Answer 19

no maximum energy for a molecule

Question 20

what does the area under the graph show (boltzmann distribution)?

Answer 20

total number of molecules

Question 21

what does it show when the curve goes through (0,0) (boltzmann distribution)?

Answer 21

no molecules = zero energy

Question 22

what does the shaded area after the activation energy line show (boltzmann distribution)?

Answer 22

proportion of molecules with an energy greater than the activation energy

Question 23

where is the curve when the molecules are at a higher temperature (boltzmann distribution)?

Answer 23

start at same place
shifted to the right
peak lower
area the same

Question 24

what happens to the proportion of molecules with energy greater than activation energy when temperature is increased (boltzmann distribution)?

Answer 24

higher proportion of molecules with greater energy at higher temperatures

Question 25

why do molecules have a higher probable energy at higher temperatures (boltzmann distribution)?

Answer 25

highest peak is at higher energy

Question 26

what does Kc mean?

Answer 26

equilibrium constant

Question 27

what does […] mean?

Answer 27

concentration of…

Question 28

what is the formula for Kc?

Answer 28

[C] power of c x [D] power of d
–over–
[A] power of a x [B] power of b

Question 29

what does it mean if Kc is = 1?

Answer 29

position of equilibrium lies halfway between reactants and products

Question 30

what does it mean if Kc > 1?

Answer 30

equilibrium lies on the right
[products] > [reactants]

Question 31

what does it mean if Kc < 1?

Answer 31

equilibrium lies on the left
[reactants] > [products]