4.1 Rates of Reaction Flashcards
How can chemical reactions only happen?
If reactant particles collide with enough energy
What is Activation Energy?
The amount of energy needed to make particles react
What is Collision Frequency?
How often the particles collide with each other
What is Percentage Success?
What percentage of collisions have enough energy
What 4 factors effect the rate of reaction?
Collision Frequency:
- Solid surface area
- Solution concentration
Percentage Success:
- Temperature
- Catalysts
Why does a higher surface area increase rate of collisions?
- More of solid is exposed to the other particles
- So collisions frequency is higher
- Therefore more successful collisions per unit time
Why does a higher solution concentration increase rate of collisions?
- More particles per unit volume
- So collision frequency is higher
- Therefore more successful collisions per unit time
Why does a higher temperature increase the rate of collisions?
- Particles have more kenetic energy
- So percentage of collisions with enough energy is higher
- Therefore more successful collisions per unit time
Why do catalysts increase the rate of collisions?
- Provide an alternate route with lower activation energy
- So Percentage of collisions with enough energy is higher
- Therefore more successful collisions per unit time
How it increase surface area of a solid?
Cutting up or grinding
What experiment demonstrates the effect of surface area on rate?
Marble chip experiment
What is used in the marble chip experiment?
Calcium carbonate chips and hydrochloric acid
What are the control variables in the marble chip experiment?
-Mass of calcium carbonate chips
- Volume and concentration of HCl
- Temeprature
Why in solutions and gases, increasing the concentration/pressure increases rate?
- There are more particles per unit volume
- So the collision frequency is higher
- More successful collisions per unit time
How can you easily increase pressure?
Make reaction vessel smaller
What experiment demonstrates the affect of concentration on rate?
Disappearing cross experiment
What are the control variables in the disappearing cross experiment?
- Total volume of solution
- Concentration of HCl
- Temperature
How is rate calculated?
Rate = 1/time taken
What does a straight line through the origin show on a concentration-rate graph?
Rate is proportional to concentration…
Double concentration = double rate
What experiment demonstrates the effect of temperature on rate?
Magnesium and acid experiment
What are the control variables in the magnesium and acid experiment?
- Mass and surface area of magnesium
- Volume and concentration of HCl
Is rate proportional to temperature in the magnesium and acid experiment?
No
- The graph does not show a straight line
- The line does not go through the origin (as the rate isn’t zero at 0°C)
What are catalysts?
- Increase rate
Remain chemically unchanged
What experiment demonstrates the effect of different catalysts on rate?
Hydrogen peroxide experiment
