Rates of reaction Flashcards
what are three ways of measuring the rate of a reaction?
observe how quickly a precipitate forms
measure the change in mass
measure the volume of gas given off
how do you calculate the rate of reaction?
amount of product formed or reactant used
DIVIDED
time
how can the rate of reaction be measured if a precipitate is produced?
place a piece of paper with a black cross below the beaker holding the solution and observe this cross through the solution
measure how long it takes for the cross to disappear
how can you measure there is a change in mass
measure initial mass using a balance
combine reactants
measure the final mass
rate = change in mass / time
units = g/s
how can you measure the rate of reaction when a gas is given off?
add reactants to a conical flask
immediately attach a gas syringe to the conical flask with a bung to ensure minimal gas escapes
take regular measurements of the final volume of gas produced
rate = total volume of gas produced / time
units = cm3/s
how can you investigate how HCl concentration affects the rate of reaction when magnesium is added?
ges will be produced so you measure the volume of gas produced
- place the HCl in a conical flask
- add the magnesium strip and quickly fit the bung and gas syringe
- record the volume of gas collected every 10 seconds
- repeat with different concentrations of HCl
- compare the rates for each concentration
What is the equation for average rate of reaction?
Amount of reactant used or Amount of product formed DIVIDED BY the Time
What are the requirements for a reaction to take place?
two reactants must collide
The particles must also have enough activation energy in order to react together.
How do catalysts speed up reactions?
Different catalysts are needed for different reactions, but they all work by decreasing the activations energy needed for the reaction to occur. They do this by providing an alternative pathway with a lower activation energy.
How does increasing the temperature increase the rate?
1) When the temperature is increased, all the particles move faster.
2) This causes them to collide more frequently.
3) And the faster they move the more energy they have, so more collisions will be successful.
How does increasing the concentration increase the rate?
If a solution is more concentrated, there are more particles in the same volume.
Similarly, when the pressure of gas is increased, there are the same number of particles occupying a smaller space.
This makes collisions more frequent.
How does increasing the surface area speed up the rate?
If one of the reactants is solid, breaking it into smaller pieces will increase its surface area to volume ratio.
So for the same volume of the solid, the particles around it will have more area to work on - so the collisions will occur more frequently.
what does the term activation energy mean?
the minimum amount of energy required for a reaction to occur between two reacting particles
marble chips react with hydrochloric acid to produce calcium chloride, water and carbon dioxide. How could you measure the rate of reaction?
since gaseous carbon dioxide is released, the rate can be measured by using a digital balance to measure the change in mass over a period of time
marble chips react with hydrochloric acid to produce calcium chloride, water and carbon dioxide. How could the rate of this reaction be increased?
increase the surface area of the marble chips by turning them into powder
increase the concentration of acid
increase the temperature
