Kinetics 1

Question 1

effect of a change in concentration on the rate of a chemical reaction

Answer 1

the higher the concentration, the more there are in a given volume and so the more often the particles will collide

Question 2

effect of a change in temperature on the rate of a chemical reaction

Answer 2

the higher the temperature, the faster the particles move and so the greater the number of collisions. Also the energy of the particles increases, so more effective collisions take place

Question 3

effect of a change in pressure on the rate of a chemical reaction

Answer 3

More collisions take place as for a gas there are more particles in the same volume

Question 4

effect of a change in surface area on the rate of a chemical reaction

Answer 4

the reaction will occur where the two types of particle meet, at the surface, so the greater the surface area, the greater the number of collisions

Question 5

collision theory

Answer 5

In order to produce a reaction, the molecules must have the correct orientation and sufficient energy – the activation energy

Question 6

effect of a catalyst on the rate of a chemical reaction

Answer 6

provides an alternate reaction route of lower activation energy allowing more collisions to produce a reaction

Question 7

calculating rate

Answer 7

• volume of gas produced/time

- gradient of a graph

Question 8

Maxwell-Boltzmann distribution shows

Answer 8

distribution of molecular energy within a gas. The horizontal axis shows the energy level and the vertical is the number of particles that have that energy

Question 9

effect of temperature on the Maxwell-Boltzmann

Answer 9

average energy of the molecules increases the area under each curve is the same, as this represents the total number of molecules

Question 10

effect of a catalyst on the Maxwell-Boltzmann

Answer 10

As the activation energy is lowered, more molecules have sufficient energy to react

Question 11

use of a solid (heterogeneous) catalyst for industrial reactions

Answer 11

• providing a surface for the reaction
• As the molecules join onto the surface the bonds between the molecules are weakened
• the energy required to break the bonds is lowered
• so the activation energy becomes lower

Question 12

economic benefits of the use of catalysts in industrial reactions

Answer 12

• increase the rate of reaction
• reduces the temperature required for the reaction
• reducing energy costs
• some reactions would not take place without a catalyst