Topic A4 - Kinetics 1

Question 1

What is activation energy?

Answer 1

heat energy required (per mole) for a collision between 2 particles to result in a chemical reaction

Question 2

How does increasing surface area of a solid increase rate?

Answer 2

(rate is proportional to solid surface area)
-more solid particles are accessible for collisions
-collision frequency increases
-successful collision frequency increases

Question 3

How does increasing solution concentration/ gas pressure increase rate?

Answer 3

-more particles per unit volume
-collision frequency increases
-successful collision frequency increases

Question 4

How does increasing temperature increase rate?

Answer 4

-particles have more kinetic energy so move faster
-collision frequency increases
-larger fraction of collisions have energy greater than activation energy
-successful collision frequency increases

Question 5

How does a catalyst increase rate?

Answer 5

-provides an alternative route with a lower activation energy
-large fraction of collisions have energy greater than activation energy
-successful collision frequency increases

Question 6

How do you calculate rate from a curve?

Answer 6

draw a tangent to point of interest

Question 7

How do you work out average rate, using a curve?

Answer 7

total y-axis change / time

Question 8

Give 3 discrete ways of measuring rate of this reaction: thiosulfate + acid

Answer 8

-time taken for bubbles to stop being produced
-indicator colour change
-disappearing cross (S)

Question 9

Give 3 continuous ways of measuring rate of this reaction: thiosulfate + acid

Answer 9

-pH change, using pH probes (pH would increase)
-volume of sulphur dioxide produced (would increase)
-conductivity change (would decrease)

Question 10

What is the distribution of energies in a collection of particles called?

Answer 10

Maxwell-Boltzmann distribution

Question 11

What does the area under the curve of a Maxwell-Boltzamann distribution mean?

Answer 11

total number of particles

Question 12

At a higher temperature, how does this effect the Maxwell-Boltzmann distribution?

Answer 12

-peak is further right
-peak is lower
-graph drops slower
(area under graph at energy greater than activation energy is bigger)

Question 13

With the addition of a catalyst, how does this effect the Maxwell-Boltzmann distribution?

Answer 13

area under the curve at energy greater than activation energy with a catalyst is bigger (no shift in curve peak, just shift in activation energy)