Kinetics 1

Question 1

Before two particles can react they have to…

Answer 1

… undergo a collision - only certain collisions produce a reaction.

Collisions must have correct orientation, energy =/> Ea

Question 2

Factors affecting rate of reaction

Answer 2

1) concentration
2) gas pressure
3) temperature
4) surface area
5) catalysts

Question 3

How does concentration affect rate of reaction

Answer 3

• more particles per unit volume

* more collisions per unit time

Question 4

How does gas pressure affect rate of reaction?

Answer 4

• more particles per unit volume

* more collisions per unit time

Question 5

How does temperature affect rate of reaction?

Answer 5

• higher kinetic energy
• particles move faster and therefore collide more
• collisions occur with greater energy and therefore a higher proportion are successful

Question 6

How does SA affect rate of reaction?

Answer 6

greater number of collisions because reactions occur where particles meet

Question 7

How do catalysts affect rate of chemical reaction?

Answer 7

• provide alternative route for reaction with lower Ea
• more successful collisions
• provide a surface for reactions
• by joining onto the surface, the bonds in the molecules are weakened; Ea is lowered
• since molecules are absorbed in the surface, they become closer, allowing them to make contact; aids reaction
• useful in chemical industry

Question 8

Maxwell-Boltzmann distribution

Answer 8

• y-axis = number of molecules
• x-axis = molecular energy

At higher temperature, the average energy of the molecules increases. Area under each curve is the same, as this is the total number of molecules

Question 9

Activation energy

Answer 9

• during a reaction, bonds must first be broken; requires energy to be taken in
• when molecules collide and react, they move through a state of high potential energy; an energy barrier

Question 10

Heterogeneous catalysts

Answer 10

• catalysts un a different phase to the reactants

* usually a solid to a gas

Question 11

Haber process

Answer 11

• combined hydrogen and nitrogen to produce ammonia
• reversible; forward reaction is exothermic
• low temperature favours ammonia formation
• N_=N causes very high Ea (high temp needed for reasonable rate)
• iron catalyst reduces Ea, allowing process

Question 12

H2SO4 production

Answer 12

Vanadium peroxide catalyst

Question 13

Ammonia production

Answer 13

Iron catalyst