15.3 1 Heterogeneous catalysis

Question 1

Heterogeneous catalyst

Answer 1

one in a different phase from that of the reactants

Question 2

what is typically used as a solid catalyst

Answer 2

transition metals and their compounds

Question 3

oxygen gas

Answer 3

can be produced by decomposing hydrogen peroxide solution (H2O2) using manganese (IV) oxide

Question 4

how are solid catalysts usually used

Answer 4

finely divided form as small particles including powder to maximise surface area
sometimes they are used instead as a thin coating on an inert support material

Question 5

sulfuric acid (H2SO4)

Answer 5

Large quantities produced as used in a large number of industries
biggest single use is in the manufacture of fertilisers

Question 6

Contact process

Answer 6

used to manufacture sulfuric acid
key reaction in process is the conversion of sulfur dioxide to sulfur trioxide
2SO2+O2 <> 2SO3

Question 7

How is the contact process achieved

Answer 7

at temperatures and pressures used in process all the substances are in the gas phased
mixture of reactants is passed over catalyst of vanadium (V) oxide V2O5 also known as vanadium pentoxide– A SOLID

Question 8

aDsorption

Answer 8

One or more reactants becomes attached to the surface of a catalyst ( don’t want bonded!)

Question 9

reaction

Answer 9

can take place following the weakening of bonds in the adsorbed reactants

Question 10

desorption

Answer 10

the reaction product becomes detached from the surface of the catalyst

Question 11

Surface adsorption theory

Answer 11

Adsorption-reaction-desorption

Question 12

Part 1 of the contact process

Answer 12

Sulfur dioxide adsorbs onto the vanadium (V) oxide and a redox reaction occurs
V2O5+SO2=V2O4+S03
vanadium goes from +5 to +4
sulfur trioxide desorbs

Question 13

Part 2 of contact process

Answer 13

oxygen reacts with the V2O4 on the surface of the catalyst and another redox reaction occurs
V2O4+1/2O2=V2O5
original catalyst regenerated
+4 to +5

Question 14

catalytic converters

Answer 14

convert emitted pollutant gases from vehicle exhausts

Question 15

carbon monoxide

Answer 15

toxic gas interferes with oxygen transport

forms through incomplete combustion of hydrocarbon fuels

Question 16

nitrogen monoxide

Answer 16

easily oxidised in atmosphere to nitrogen dioxide where can be a respiratory irritant and contribute to formation of acid rain
forms through reaction between nitrogen and oxygen that exist in an internal combustion engine

Question 17

main transition metals used in catalytic converters

Answer 17

platinum and rhodium and sometimes palladium

Question 18

process in catalytic converters

Answer 18

molecules of carbon monoxide and nitrogen monoxide are adsorbed onto surface bonds are weakend react together to from carbon dioxide and nitrogen then desorb
2CO+2NO=2CO2+N2