Topic 6 Flashcards
What must particles do in order to react?
Collide
With enough energy
And the correct orientation
What 4 things does rate of reaction depend on?
Temperature
Concentration/ pressure
Surface area
Catalyst
How do you measure rate of reaction?
Amount of reaction used or product formed
Divided by time
How do you measure rate of reaction with a colour change test?
What is the drawback?
Observe a cross through the solution in a beaker or conical flask
Measure how long it takes to disappear
Faster it disappears the quicker the reaction
Results are subjective- different people might not agree over the exact point when the mark disappears
You can’t plot a rate of reaction graph from it
What equipment is needed for a change in mass measuring of rate of reaction?
What equipment is needed for volume of gas measuring of rate of reaction?
Balance/scales
Stopwatch
Gas syringe
Stopwatch
What rate experiments can we use for volume of gas?
How do you it?
Magnesium and HCL react to produce H2 gas
Add a set volume of dilute HCL acid to a conical flask
Add some magnesium ribbon and quickly attach a gas syringe to the flask
Start stopwatch and take readings of volume of gas at regular intervals
What rate experiments can we use to produce a precipitate?
How do you it?
Sodium Thiosulphate and HCL produce a cloudy precipitate
Both chemicals are clear and react to form a yellow precipitate of sulphur
Add a set volume of dilute sodium thiosulphate to a conical flask
Place flask on a piece of paper with a cross on it
Add some dilute HCL and start the stopwatch
Time how long it takes the cross to disappear
Define equilibrium…
What is a closed system?
The rate of the forwards reaction in a closed system is equal to that of the backwards reaction
No matter can escape only energy
What does it mean if equilibrium lies to the right?
What does it mean if equilibrium lies to the left?
What does the position of equilibrium depend on?
The concentration of the products is greater than reactants
The concentration of the reactants is greater than the products
Temperature
Pressure
Concentration
Give an example of a reversible reaction in which the forwards reaction and backwards reaction are endothermic and exothermic…
If you heat blue hydrated copper(II) sulphate crystals it leaves white anhydrous copper(II) which is endothermic
If you then add a couple drops of water to the white powder the blue crystals come back again which is exothermic
What is Le Chatelier’s principle?
If a closed system at equilibrium experiences a change the system will act to counteract that change
How does Le Chatelier’s principal link to change in temperature?
If you decrease the temperature the equilibrium will move in the exothermic direction to produce more heat
You’ll get more products for the exothermic reaction and fewer products for the endothermic reaction
How does Le Chatelier’s principal link to pressure?
Only involves gases
Increasing pressure makes the equilibrium try to reduce it- moves in the direction where there are fewer molecules of gas
A balanced symbol equation shows which side has more molecules of gas
How does Le Chatelier’s principal link to concentration?
Changing concentration will mean that the system will no longer be at equilibrium
The system responds to bring itself back to equilibrium
If you increase concentration of the reactants the system tries to decrease it by making more products
If you decrease concentration of the products the system tries to increase it again by reducing the amount of reactants
