Rates Of Reaction & Energy Changes Flashcards
Name 3 methods determining rates of reactions
Precipitation
Changes in mass (gas given off)
The volume of gas given off
Describe the precipitation method
Mixing 2 transparent solutions
Solution will start to go cloudy (producing a precipitate)
Measure how loving it takes for the solution to go cloudy
(Faster it disappears, after the reaction)
Name 2 solutions you could use for the precipitation experiment
Hydrochloric acid
Sodium thiosulphate
Describe the ‘change in mass’ experiment?
Mix a solution and solid
When gas is released, the lost mass can be measured
The quicker the reading on the balance drops, the faster the reaction
The reaction finishes when the reading stops
If harmful gases are given off during the ‘change in mass experiment’ what do you do?
Do the experiment is a fume cupboard
Describe the experiment when it shows you the volume of gas given off
Involves a gas syringe (measuring volume of gas given off)
The more gas given off during a set interval, the faster the reaction
Name 4 ways you can measure temperature change
Salt dissolving in water
Neutralisation reaction
Displacement reaction
Precipitation reaction
Describe salt dissolving in water reaction
Add salt to polystyrene cup of water
Measure change in temperature using thermometer
Describe neutralisation reaction
Mixing acid and base —> salt and water
What kind of reaction is neutralisation reactions
Exothemric
Describe displacement reactions
More reactive element displaces less reactive element in a compound
What kind of reaction is displacement reactions?
Exothermic
Describe precipitation reactions
2 solutions mixing producing precipitates
What kind of reaction are precipitation reactions?
Exothemric
Define precipitate
An insoluble salt
What does the rate of reaction depend on?
Collision frequency
More successful collisions = faster reaction
Define collision frequency
How often particles collide
What are the components of the collision theory?
Temperature
Concentration
Surface area
What does an increasing temperature do to a reaction?
Increases rate of reaction
Particles move faster = more collisions + energy of collisions
Therefore more successful collisions
What does increasing concentration do to a reactions?
Increases rate of reaction
Solution = more particles in fixed volume = more successful collisions
Gas(high pressure) = particles are more crowded = more successful collisions
What does an increasing surface area do to a reaction?
Increases rate of reaction
Solid reactant breaks into smaller pieces
Increasing surface are to volume ratio
Particles will have for surface area = more successful collisions
Define successful collisions
More parties will collide with enough energy to react
Define catalyst
A substance which increases rate of reaction whiteout being chemically changed or used up in a reaction
What does a catalyst do in terms of activation energy?
They decrease activation energy
They provide an alternative reaction pathway, that has a lower activation energy
Define enzymes
Biological catalysts
What are enzymes involved in?
Production of alcoholic drinks
Using enzymes from yeast cells
Define activation energy
Minimum amount of energy needed for a bond to break
Describe endothermic reactions
Takes in energy from its surroundings
How are endothermic reactions shown?
In a fall in temperature
Example of endothermic reaction
Breaking bonds
Describe exothermic reaction
Gives out energy to its surroundings
How are exothermic reactions shown?
Rise in temperature
Example of exothermic reaction
Making bonds
Equations for overall energy change
Energy required to break bond - energy released by forming bonds
Unit for energy change
KJ mol -1
