rate of reactions - unit 3 AOS 2

Question 1

collision theory

Answer 1

1. reactants must physically collide with each other
2. reactants must collide with enough energy to break the bonds
3. reactants must collide with correct orientation

Question 2

activation energy

Answer 2

• the minimum energy of a collision required to break the bonds of reactants, allowing the reaction to begin

Question 3

measuring reaction rate

Answer 3

• for reactions involving changes in heat energy a thermometer can be used
• the formation of a precipitate can be measures
• change in colour
• volume of gas

Question 4

effect of temperature on reaction rate

Answer 4

• as the temperature of a reaction system increases, so does the rate of reaction
• reactants have increased kinetic energy and so collide more frequently
• more reactants will collide with an energy equal to or higher than the activation energy , increasing the percentage of successful collisions (correct orientation)
• more bonds will be broken at a given period of time

Question 5

effect of surface area on rate of reaction

Answer 5

• as the the surface area of reactants increases, so does the rate of reaction
• more reactant particles are exposed to each other, producing more collisions
• more collisions means there will be an increase in the number of successful collision in a given period of time

Question 6

the effect of pressure on rate of reaction

Answer 6

• as the pressure increases, so does the rate of reaction
• increased pressure means there is a decreased volume so there is more crowding of particles, increasing the number of particles per unit of volume.
• as particles are more crowded together, there is an increase in frequency of collisions
• this increases the amount of successful collisions over a given period of time.

Question 7

the effect of concentration on reaction rate

Answer 7

• as the concentration of reactant increases, so does the rate of reaction
• there are more particles present per unit volume
• more reactant particles come into contant with each other increases the frequency of collisions
• this increases the percentage of successful collisions

Question 8

catalysts

Answer 8

• a substance used to create an alternative reaction pathway with a lower activation energy, thus decreasing the amount of energy needed to break the bonds, increasing the rate of a reaction

Question 9

effect of catalysts on the rate of reaction

Answer 9

1. catalysts increase the rate of reaction
2. catalyses provide an alternative reaction pathway with a lower activation energy so less energy is required to initiate the reaction
3. particles are more likely to collide with sufficient energy that exceeds the activation energy
4. this means the bonds of the reactants are broken more frequently and products are formed, increasing the rate of reaction.

• a catalyst only increases the rate of reaction, not the yield
• the enthalpy of the reactants and products are still the same. the delta H value does not change.

Question 10

heterogenous catalyst

Answer 10

• catalysts in a different physical state to the reactants and products

Question 11

homogenous catalyst

Answer 11

• catalysts in the same physical state as the reactants and products

Question 12

closes system

Answer 12

• a system in which energy can enter or leave, but matter cannot

Question 13

open system

Answer 13

• a system in which both matter and energy can enter or leave