Rate and Extent of Chemical Change Flashcards
What is the rate of a chemical reaction?
How quickly the reactants are changed into products
Example of slow reactions:
Rusting of iron
Chemical weathering
Example of moderate reactions:
Metal magnesium with an acid (produce a gentle stream of bubbles)
Example of fast reactions:
Burning
You can find the speed of reaction by recording…
CLUE: 2 ways
The amount of product formed over time
The amount of reactant used up over time
On a graph, what type of reaction becomes flat in the least time?
The fastest reactions
What is the collision theory?
That during a chemical reaction, particles must collide in order to react
What does the rate of chemical reaction depend upon?
CLUE: 2 things
The collision frequency of reacting particles - the more collisions the faster the reaction
The energy transferred during collision - particles have to collide with enough energy to be successful
What is the activation energy?
The minimum amount of energy needed, to break the bonds in the reactants and start the reaction
What does an increase in the number of collisions or amount of energy particles collide with do?
It increases the rate of reaction
What 4 factors affect the rate of reaction?
Temperature
Concentration of a solution or Pressure of a gas
Surface area
Presence of a catalyst
How does an increase in temp increase the rate of reaction?
The particles move faster - collide more frequently
More energy - more collisions have enough energy to make reaction happen
How does an increase in concentration or pressure increase the rate of reaction?
Concentration - more particles in same volume
Pressure - same number of particles in smaller space
Bothe mean collisions are more frequent
How does an increase in surface area increase the rate of reaction?
Increase SA:volume ratio
For same volume of solid, particles around it will have more area to work on - collisions more frequent
What is a catalyst?
Something that speeds up the rate of reaction without being used up
How do catalysts work?
They decrease the activation energy needed for the reaction to occur by providing an alternative pathway with a lower activation energy
How are catalysts beneficial?
Save money - less heat/energy needed because they lower temperatures needed
Chemicals made quickly - money made faster
Reusable
Less pollution - less fossil fuels being burnt
What is the equation for rate of reaction?
Time
How can you measure the rate of reaction?
Precipitation and Colour change
Change in Mass
Volume of Gas given off
How to find the mean rate?
Total time taken for the reaction
How to find rate from a graph?
Draw a tangent, find the gradient of the tangent
If we are investigating the effect of one factor, what do u have to do with other factors?
Keep them controlled
