What experiments can you do to follow the rate of reactions?
- a rate of reaction that produces gas can be observed by measuring how quickly gas is produced:
- measure the change in mass while the experiment is happening, mass will fall as gas is released, take readings of mass at regular time intervals
- measure volume of gas given off in a gas syringe at regular time intervals
What does rates of reactions depend on?
- collision frequency of reacting particles (more collisions, faster reaction)
- energy transferred during collisions (particles have to collide with enough energy for a collision to be successful)
How the amount of product determined?
-depends on the amount of reactant started with
-more reactant means more particles, which will have more reactions so more product
-total amount of product is directly proportional to limiting reactant
once all the limiting reactant is used up the reaction can’t continue, even if some reactants are in excess
How is the rate of reaction increased?
-by more collisions
What does the rate of reaction depend on?
- temperature
- concentration
- size of particles
- prensence of catalyst
How does concentration (pressure) affects the rate of reaction?
- more concentrated solutions have more particles of a reactant in the same volume)
- making collisions more likely
- increasing pressure in a gas means molecules are more crowded , so frequency of collision increases
How does temperature affects the rate of reaction?
- temperature increase means particles move faster, moving quicker means more collisions
- temperature increase, increases the energy in collisions (since particles move faster) meaning more particles will collide with enough energy to make reactions happen
How does a catalyst affects the rate of reaction?
- increases number of successful collisions
- gives reacting particles a surface to stick to where they can collide with each other (reducing the energy needed to react before)
- number of collisions isn’t increased, but successful collisions are
How does the size of particles affects the rate of reaction?
- breaking a solid reactant into smaller solid particles increases surface area
- particles around it have more area to work on, so collision frequency increases
What are limiting reactants?
-the reactant being totally used up
What are reactants in excess?
-reactants left behind at the end of a reaction
Why do factories making fine powders have to be careful?
- fine powders of combustible materials disperse in air and burn incredibly fast because of the big surface area
- if there’s a spark they explode (very fast reaction that releases lots of gaseous produces very quickly)
