the rate and extent of chemical change

Question 1

what does the rate of chemical reactions mean

Answer 1

the speed at which the reactants get turned into products

Question 2

what is the equation to work out the average rate of reaction

Answer 2

rate of reaction = quantity of reactants used / time taken (for change to occur)

OR
rate of reaction = rate of products formed / time taken

Question 3

how do you calculate the rate of reaction at a specific time from a graph

Answer 3

calculate the gradient of the curve at the point asked for (for example 2 minutes) using a tangent remember gradient = change in y / change in x

Question 4

what happens to the mass of reactants when they are first combined together compared to near the end of the reaction

Answer 4

the mass of the reactant would fall rapidly at first and then slow as the reaction progresses as it gets used up

Question 5

what are the main factors that effect the rate of reaction

Answer 5

pressure/concentration , temperature, surface area, catalyst

Question 6

what is the collision theory

Answer 6

in order for particles to react they have to collide with each other with sufficient energy

Question 7

define activation energy

Answer 7

the minimum energy required for a reaction to take place between reacting particles

Question 8

what are the two general factors that the rate of reaction depend on if we think about a reaction including tons of particles

Answer 8

1. the amount of energy the particles have
2. the frequency of collisions

Question 9

how does temperature effect the rate of reaction

Answer 9

as temp increases the particles gain more energy meaning they move faster therefore they will collide more frequently and with more energy and therefore are more likely to reach their activation energy.

higher rate of successful collisions and higher rate of reaction

Question 10

how does concentration and pressure effect the rate of reaction

Answer 10

when increased there will be more particles per unit of volume making collisions more frequent increasing the rate of reaction

Question 11

how does surface area effect the rate of reaction

Answer 11

higher surface area will increase the rate of reaction as there is more space for other reactants to collide, increasing the frequency of collisions leading to a higher rate of reactions

Question 12

what are catalysts

Answer 12

substances that speed up a reaction without being used up in the reaction itself

Question 13

how do catalysts effect the rate of reaction

Answer 13

they lower the activation energy by offering an alternate reaction pathway therefore there will be more successful collisions

Question 14

what do reaction profiles show

Answer 14

the change in the chemicals energy during a reaction

Question 15

what is meant by a reversible reaction

Answer 15

the products of a reaction can react to reform the reactants

Question 16

if a reversible reaction is exothermic in one direction what will happen in the other direction

Answer 16

it will be endothermic

Question 17

what happens if we heat hydrated copper sulphate

Answer 17

it will react to form anhydrous copper sulphate and water. we can then take the products and react them back to form hydrated copper sulphate. this is exothermic and will release heat

Question 18

define the point of equilibrium

Answer 18

when the forward and reverse reaction take place at the same rate in a closed system

Question 19

what is meant by the position of equilibrium

Answer 19

if there are more products formed than reactants in a reversible reaction at one point in time the equilibrium will be shifted to the right

Question 20

how can the position of equilibrium change

Answer 20

dependent on the conditions such as temperature

Question 21

what is le chateliers principle

Answer 21

if you change the conditions of a reversible reaction, the position of equilibrium will shift to try and counteract that change

Question 22

what is the effect of changing the temperature on equilibrium if the forward reaction was exothermic

Answer 22

if we decreased the temperature of the system the equilibrium will move in the exothermic direction ( right) in order to release heat energy and counteract the change. equilibrium will then more to right and we would have more products.

increase temp = opposite

Question 23

what is the effect of changing the pressure on equilibrium

Answer 23

if we increased pressure, equilibrium will more to whichever side that reduces the pressure back down ( the side with the least number of molecules as pressure is how many particles)

decrease = opposite

Question 24

what is the effect of changing the concentration on equilibrium

Answer 24

if add more reactants it will increase concentration and will shift to the right to form more products