Rates of Reaction Flashcards
What is a rate of chemical reaction?
How fast reactants are changed into products?
Give examples of a slow, moderate speed and fast reaction
Slow - rusting
Moderate speed - Magnesium+ acid
Fast - burning / explosions
How can you calculate the speed of a reaction?
Amount of product formed/used
—-—————————-
Time
On a graph, the steeper the line, the faster the rate of reaction. Overtime the line becomes less steep what does this indicate?
The reactants are used up
What is the collision theory?
Particles must collide with enough energy in order to react.
What is collision frequency?
How often the particles collide. The more collisions there are, the faster the reaction.
What is the rate of chemical reaction dependent on?
Collision frequency
Energy transferred during a collision
What is the minimum amount of energy that particles need to react called?
Activation energy
Why do particles need activation energy?
To break the bonds in order to react and start the reaction
What factors increase the number of collisions in a reaction?
The amount of energy particles that collide. An increase in the number of collisions increases the rate of reaction
Name four things that affect the rate of reaction
1) Temperature
2) Concentration of a solution/pressure of gas
3) Surface area
4)Presents of a catalyst
What happens when the temperature is increased in a reaction?
When the temperature is increased, the particles have more energy and move faster so have more collisions.
What happens when the concentration or pressure is increased in a reaction?
If a solution/gas is more concentrated, it means there are more particles of reactant in the same volume so collisions are more likely so the reaction rate increases
What happens when the surface area is increased in a reaction?
The rate of reaction increases if one reactant is solid and breaks into smaller pieces therefore increases its surface area so the surface area to volume ratio is increased
What is the calculation for measuring the rate of a reaction?
Name three different ways that the rate of reaction can be measured
1) precipitation
2) change in mass
3) volume of gas given off
Explain how a rate of reaction can be measured through precipitation
1) mix two see through solutions in a flask
2) Put the flask on a piece of paper that has a mark on it
3) observe the mark through the mixture and measure how long it takes for the mark to be obscured. The faster the mark disappears, the faster the reaction.
What is the potential problem with measuring a rate of reaction through precipitation?
The result is subjective - different people might not agree on exactly when the mark disappears
Explain how to measure the rate of reaction through the change in mass
1) mix two solutions in a flask.
2) put the flask on a mass balance and take a reading
3) You know the reaction has finished when the reading on the balance stop changing
4) you can plot a graph of change in mass against time
Explain how to measure the rate of reaction through the volume of gas given off
1) mix two solutions in a flask and attach a gas syringe
2) measure the amount of gas given off at set time intervals
3) you can tell the reaction is finished when no more gas is produced
4) you can plot a graph of gas volume against time elapsed
How can you measure how surface area affects the rate of reaction?
1) add marble chips CaCO3 and dilute HCl to a flask
2) add a gas syringe
3) measure the volume of gas (CO2) produced at regular intervals
4) plot the results on a graph - time on x axis and volume on y axis
5) repeat the experiment but this time with the marble chips more crunched up
Finer particles of a solid in a rate of reaction experiment means a ________ rate
Higher
Give examples catalysts which can be used to speed up a rate of reaction experiment
Manganese (IV) oxide MnO2
Copper (II) oxide CuO
Zinc oxide ZnO
