The Rate and Extent of Chemical Change Flashcards
What is an example of a slow reaction?
The rusting of iron
What is an example of a moderate speed reaction?
Magnesium reacting with acid to create a gentle stream of bubbles
What is an example of a fast reaction?
Burning or an explosion
How do you find the rate of a reaction?
By recording the amount of product formed or the amount of reactant used
How is the rate of a reaction represented on a graph?
Steep line = faster rate
Less steep line = slower rate
What does collision theory state?
A higher collision frequency of particles results in a faster reaction.
What is activation energy?
The minimum amount of energy that particles need for a successful collision
What are the four factors that can affect the rate of reaction?
Temperature, surface area, pressure/concentration, catalysts
How does temperature affect the rate of reaction?
Increased temperature gives the particles more energy so they move faster which increases the number of successful collisions
How do pressure and concentration affect the rate of a reaction?
More particles being present within a certain volume increases the likelihood of frequent successful collisions
How does surface area affect the rate of reaction?
Breaking a solid reactant into more, smaller pieces increases its surface area to volume ratio which gives the particles around it more area to work on
How does using a catalyst affect the rate of a reaction?
It speeds up the reaction without being used. It decreases the activation energy by providing an alternative reaction pathway
How can you visually measure the rate of a reaction?
- turns from transparent to cloudy
- out a mark under the solution and see how long it takes to disappear
- see how long it takes for the solution to lose of gain colour
How can you measure the rate of a reaction based on the change in mass (gas given off)?
Use a mass balance. As the gas is released, loss of mass is shown on the balance. The quicker the reading drops, the faster the reaction. Take regular readings to plot a graph. Very accurate.
How do you measure the rate of a reaction based on the volume of gas given off?
Use a gas syringe. The more gas given off in a certain time period, the faster the reaction. Take regular readings to plot a graph. A vigorous reaction can blow the plunger out of the syringe.
What do Magnesium and HCl react to produce?
Hydrogen (H2)
How do you react Magnesium with HCl?
- add HCl to a conical flask on a mass balance
- add magnesium ribbon and plug with cotton wool
- time it and take readings at regular intervals
- record and plot the results
- repeat with different concentrations of acid solutions
What is the result of reacting Sodium Thiosulfate and HCl?
They are both clear solutions and they react together to form a yellow precipitate of sulfur
How do you react Sodium Thiosulfate and HCl
- add dilute sodium thiosulfate to a conical flask on top of a cross drawn on paper
- add some dilute HCl
- time how long it takes for the solution to cloud until you can’t see the cross anymore
- repeat with different concentrations
What is the formula to calculate the mean rate of a reaction from a graph using two points?
Change in y / Change in x
How do you find the rate of a reaction at a particular point on a graph?
Draw a tangent at the point and calculate it’s gradient
What happens to the concentrations of reactions and products during a reversible reaction?
The concentration of the reactant falls, slowing the forward reaction down. The concentration of the product rises, speeding up the backwards reaction.
What is equilibrium?
When the forward and backward reactions are going at exactly the same rate and have reached a balance. This means that even though the reactions keep happening, there is no overall change.
What is the most important condition for equilibrium in a reversible reaction.
That it takes place in a closed system, where none of the reactant of products can escape.
