6 Rate and exchange

Question 1

Exothermic Reaction

Answer 1

a reaction which transfers energy to it’s surroundings usually in the form of heat

Question 2

endothermic reaction

Answer 2

a reaction which absorbs energy from its surroundings usually in the form of heat

Question 3

rate of reaction (g/s)(cm³/s) =

Answer 3

amount of reactant used or amount of product formed (cm³/g) /
time (s)

Question 4

rate of reaction def

Answer 4

how fast reactants are changed into products

Question 5

what is the activation energy

Answer 5

minimum amount of energy that particles need to for bonds to break and particles to react

different for each reaction

Question 6

what is collision theory

Answer 6

Particles must react with enough energy in order ot react

Question 7

factors affecting rates of reaction

Answer 7

• temperature
• concentration of a solution (liquid)
• pressure in a surface area (gas)
• pressence of a catalyst

Question 8

how does temperature affect rate of reaction

Answer 8

• when temp increases particles gain more kinetic energy so they move faster
• If they are moving faster there will be more frequent collsions increasing frequencey of succesful collsions with the activation energy
• therfore a higher rate of reaction

Question 9

how does concentration and pressure affect rate of reaction

Answer 9

• if a solution is more concentrated there are more particles colliding in the same volume as solvent
• if pressure of a gas is increased there are same amount of particles in a smaller space
• this makes collisions more frequent therefore the frequncey of succesful collisons increases which are meeting the activation energy therefore a higher rate of reaction

Question 10

How does surface area affect the rate of reaction

Answer 10

• higher surface area increases surface area to volume ratio therefore there is more surface area for particles to collide with
• for the same volume of solid, particles around will have more area to collide with
• therefore number of collisions high therefore frequency of successful collisions which reached their activation energy is higher
• therefore higher rate of reaction

Question 11

how does the use of a catalyst affect the rate of reaction

Answer 11

• a catalyst lowers activation energy by providing an alternative reaction pathway
• so particles need a lower energy to reach their activation energy making it easier to reach this activation energy
• therefore more frequent successful collisions therefore higher rate of reaction
• catalysts dont get used up in reactions

Question 12

reaction pathway diagram/graph exothermic

Answer 12

• energy on y axis, progress of reaction on x axis
• reactants start high product is low
• activation energy from reactant line to top - arrow up
• energy change from reactant line to product line - arrow down
• if drawing reaction path with catalyst make the curve of activation energy smaller than normal
• reaction pathways!

Question 13

reaction pathway diagram/graph endothermic

Answer 13

• energy on y axis, progress of reaction on x axis
• reactants start low product is high
• activation energy from reactant line to top - arrow up
• energy change from reactant line to product line - arrow up
• if drawing reaction path with catalyst make the curve of activation energy smaller than normal
• reaction pathways!

Question 14

what happens as reactants react

Answer 14

their concentration falls so the forward reaction will slow down

Question 15

what happens as more product is formed

Answer 15

their concentration rises so the backwards reaction will speed up

Question 16

what is equilbirum

Answer 16

• when the forwards and backwards reaction at occurring at the same rate
• both reactions ate still happening bute there is no overall effect