Rates Of Reaction Science Flashcards
What is the energy particles must have to react
Activation energy
What does a catayls do in a experiment
A catalyst lowers the activation energy increasing the rate of a reaction without being used up
How does a catalyst work
They lower the activation energy e.g. provide a surface are for the reactants to bind to
When concentration increase explain why the rate of reaction increases
There are more particles in the same volume so collisons are more frequent
What would not speed up the chemical reaction
Increasing the particle size
Rate of reaction products formed equation
To do this equation you need to divide quantity of products formed by time taken and your units will be cm3/s for example 180cm3 of hydrogen gas in 2 mins because hydrogen is a product you do 180cm3 divided by 120s=1.5cm3/s
Reactans used equation
To do this you will need to do reactants used suchas grams and divide it by time taken for example 3g of magnesuim takes 4 mins to dissapear which means you have to do divide 3g by 240s=0.0125g/s
To find out moles
You have to do this for example 0.6 moles in 2 minutes you need to do 2 divide by 0.6 which =0.3mol/min
State one change that could be made to give more accurate results
Use a pipet to measure acid
What property of hydrogen does this method of gas collection depend
Liquid property
State two variables that must be kept constant to make the investagtion fair
Same amount of acid
Amount of magnesuim
What is a control variable
A control variable is an experimental condition or element that is kept the same throughout the experiment
Dependent
The dependent variable is the measure
Independent variable
The variable you change
Collision theory
For particles to react they have to colldie with each other with sufficient (activation energy)
Recall a definition for rate of reaction.
the speed at which a chemical reaction takes place
Explain how there can be different units for measuring
rate of reaction.
Either cm3/s or g/s
List some factors that can affect the rate of a chemical
reaction.
temperature.
concentration.
particle size.
use of a catalyst.
What happends if the tempreture increases
As the tempretue increases particles gain more energy which means they move faster collide more frequently and more likely to exceed activation energy and has a higher rate of reaction
What does concentration/pressure do
Concentration/pressure when either is increasd means there will be more particles per unit of volume make the collisons more frequnet and increases the rate of reaction
What does surface area do
A solid block of mg or small chunks powder is best because it has the highest surface area and the frequency would be higher which would increase the rate of reaction
Tangents
Draw a straight line just touching the curve and the you have to find out the change in the volume of hydrogen divided by change in time the make your line longer so it hits one of the number on the left then trace the other end of it to another number on the left then bring it down to the bottom numbers find the diffrence by subtracting between the two numbers on the left then find the time on the number at the bottom then divide
Use collision theory to explain how changing temperature
alters the rate of reaction.
With an increase in temperature, alters it due to increasing the kinetic energy causing particles to bounce around faster and more succesful collsions
Use a graph to calculate the rate of reaction at specific
times in a chemical reaction.
change in concentration/change in time
State how collision theory explains the effect of surface
area on the rate of reaction
If the surface area of a reactant is increased: more particles are exposed to the other reactant. there is a greater chance of particles colliding, which leads to more successful collisions per second.
Calculate the surface area to volume ratio.
divide the surface area by the volume.
Use collision theory to explain how changing the
concentration alters the rate of reaction.
Changing the concentration More collisions mean a faster reaction rate.
Use collision theory to explain how changing the pressure
of gaseous reactants alters the rate of reaction.
If the pressure of gaseous reactants is increased, there are more reactant particles.
Interpret graphs involving rates
The steeper the faster and curve less steep reaction slower and when its flat the reactions over
