Paper 2: Rates of reaction

Question 1

How is rate of reaction calculated

Answer 1

Reactant/product used or formed/time

Question 2

Units for rate of reaction

Answer 2

g/s cm3/s or mol/s

Question 3

3 ways of meausring rates of reaction

Answer 3

-Loss of mass of reactions
-Volume of gas produced
-Time for a solution to become opaque

Question 4

Describe measuring rate by measuring mass loss

Answer 4

-Place reaction flask on balance
-A gas is given off, so record the decrease in mass in time intervals
-Plot a graph of mass vs time

Question 5

Describe measuring rate by monitoring volume of gas

Answer 5

-Connect a gas syringe to a reaction flask and measure volume of gas formed in intervals
-Plot a graph of volume vs time

Question 6

Describe measuring rate by monitoring the disappearance of a cross

Answer 6

-Take a piece of paper and mark a cross on it. Put reaction flask on this cross. Measure the reagants and measure how long it takes for a cloudy mixture to conceal a cross

Question 7

How to find rate of reaction and some time from a graph

Answer 7

-Pick a point corresponding to the time, and find the tangent to the curve at this point
-The tangent is the gradient the steeper the tangent the faster the rate

Question 8

Factors affecting rate of a chemical reaction

Answer 8

-Conc of reactants
-Pressure of gases
-Surface area
-Temperature
-Catalysts

Question 9

What is collision theory

Answer 9

Chemical reactions can occur only when reacting particles collide with each other with sufficent energy

Question 10

Effect of increasing temperature on rate of reaction

Answer 10

-Kinetic energy increases
-Particles move faster
-Collide more frequentley/higher chance of collisions

Question 11

Effect of increasing concentration on rate of reaction

Answer 11

conc increases=faster reaction
more reactants=more frequent collisions

Question 12

Effect of the increasing pressure of a gas on the rate of reaction

Answer 12

-Increases number of gas molecules so increases frequency of collisions and the rate of reaction

Question 13

Effect of increasing the surface area on rate of reaction

Answer 13

-A greater surface area increases frequency of collisions and rate of reaction

Question 14

How does a catalyst affect the reaction profile?

Answer 14

-increases reaction by providing a different pathway for a reaction that has a lower activation energy
-Reaction profile for a catalysed reaction will have a lower maximum of the curve (lower activation energy)

Question 15

What is a reversible reaction

Answer 15

Reaction can react backwards to produce the original reactants

Question 16

When is dynamic equilibrium reached

Answer 16

-When the forward and reverse reactions occur at the same rate and the concentrations of reactants and products remain constant

Question 17

Le Chatelier’s principle

Answer 17

If a system is at equilibrium and a change is made to any of the conditions, the system responds to conteract the change and restore equilibrium

Question 18

Effect of changing concentration of reactant and product on position of the equilibrium

Answer 18

-More products will be formed until equillibrium is reached again

Question 19

Effect of changing temperature of reactant and product on position of the equilibrium

Answer 19

-Amount of products increases for an endothermic reaction
-Amount of products decreases for an exothermic reaction

Question 20

Effect of changing Pressure of reactant and product on position of the equilibrium

Answer 20

-increase in pressure causes equilibrium to shift towards the side with smaller number of molecules

-decrease in pressure causes equilibrium to shift towards side with larger number of molecules

-No effect in number of molecules equal

Question 21

Effect of a cataylst on the position of equilibrium

Answer 21

No effect
Speeds up forwards and backward reactions equally