rates of reactions

Question 1

what is the collision theory?

Answer 1

the collision theory describes the conditions required for a chemical reaction to occur

Question 2

what are the requirements for a successful collision to occur?

Answer 2

for a chemical reaction to occur,
-reactants must physically collide with each other
- reactants must collide with sufficient energy to break bonds within them (activation energy)
- reactants must collide with correct orientation for bonds to actually break

Question 3

how do the collision theory principles affect the rate of reaction?

Answer 3

they affect the rate of reaction as they explain how many moles of product will be formed/how many moles of reactants are used up in a given period of time.

Question 4

how does temperature affect reaction rate according to the collision theory?

Answer 4

temperature of substance represents average kinetic energy of the particles within the substance. as temperature increases, so does reaction rate due to reactants colliding more frequently due to increased average kinetic energy. additionally, because number of reactants with enough energy to surpass the activation energy threshold increases, the greater proportion of successful collisions (correct orientation).

Question 5

what does surface area of a reactant refer to?

Answer 5

surface area of a reactant refers to how much area a solid has available to collide with other reactants.

Question 6

how do smaller reactants affect the reaction rate?

Answer 6

smaller reactants mean that there is more overall surface area, allowing reactant particles to collide more frequently, leading to more successful collisions over a given period of time, leading to a faster reaction rate.

Question 7

what is a key feature of pressure and volume?

Answer 7

pressure and volume are inversely proportional

Question 8

how are pressure and volume inversely proportional?

Answer 8

when pressure of vessel doubles, volume halves

when pressure of vessel halves, volume doubles

Question 9

how does a decrease in volume lead to an increased rate of reaction?

Answer 9

a decreased volume leads to a smaller space, meaning there is an increase in number of reactant particles present per unit volume, which means that there is an increase in frequency of successful collisions and thus an increased rate of reaction.

Question 10

how does adding more gas particles to system increase the rate of reaction?

Answer 10

adding more gas particles to system increases the rate of reaction but only if volume and temperature are both kept constant.

Question 11

how does an increased concentration lead to a faster reaction rate?

Answer 11

an increased concentration means that more reactant particles are present in system per unit volume, meaning collision frequency increases, leading to an increased rate of reaction

Question 12

how can reaction rate be measured?

Answer 12

a change in temperature, p, mass or colour.

Question 13

what is a drawback of using measurement techniques in open systems?

Answer 13

any gas evolved during reaction can escape

Question 14

why are closed systems preferred?

Answer 14

closed system means reaction vessel is airtight, so no gas can enter or escape.

Question 15

how is gas volume measured to measure the rate of reaction in gaseuous states?

Answer 15

it is measured and recorded at fixed time intervals

Question 16

what is a transition state?

Answer 16

it refers to when activation energy is absorbed and new arrangement of atoms occurs.

Question 17

when does transition state occur?

Answer 17

it occurs at activation energy, when atoms in transition state rearrange into products as reaction progresses.

Question 18

what is the reaction rate defined as?

Answer 18

the rate of reaction is described as the measure of the change in concentration of the reactants or the change in concentration of the products per unit time

Question 19

what are catalysts?

Answer 19

catalysts interact and bind with reactants to provide an alternate reaction pathway with a lower activation energy.

Question 20

how do catalysts affect reaction rate?

Answer 20

catalysts affect reaction rate by lowering activation energy, which allows for a greater proportion of reactant particles to have the necessary activation energy to collide successfully.

Question 21

what do catalysts lower?

Answer 21

the activation energy of both the forward and reverse reactions

Question 22

what do catalysts not do?

Answer 22

they do not lower the percentage yield

Question 23

are catalysts used up?

Answer 23

no as they are chemically involved in reaction but not chemically altered, they can be physically altered

Question 24

what is a common form of catalysts

Answer 24

usually in powdered or porous form

Question 25

what are heteorgenous and homogenous catalysts?

Answer 25

heterogenous catalysts are catalysts present in a different physical state than the reactants and products

homogenous catalysts are catalysts present in a same physical state as the reactants and products