Topic 6-The Rate And Extent Of Chemical Change Flashcards
What is the rate of a chemical reaction?
How fast the reactants are changed into products.
What are slow reactions?
Rusting of iron.
Chemical weathering-acid rain damage to limestone buildings.
What are normal speed reactions?
Magnesium reacting with an acid to produce bubbles.
What is an example of a fast reaction?
Burning.
Explosions.
What allows particles to react?
How often particles collide. The more collisions the faster the reaction is.
The energy transferred during a collision.
Particles have to collide with enough energy for the collision to be successful.
What is activation energy?
The minimum amount of energy needed for particles to react.
What four things does the rate of reaction depend on?
Temperature.
Surface area.
Prescence of a catalyst.
Concentration of a solution or the pressure of a gas.
How does temperature increase the rate of reaction?
When the temperature is increased the particles move faster.
If they are moving faster they will collide more frequently.
Also they faster they move the more energy they will have so more of the collisions will have enough energy for the reaction to happen.
How does increasing the concentration or pressure increase the rate of reaction?
If a solution is more concentrated it means there are more particles in the same bolume of water.
If the pressure is increased it means the same number of particles occupy a smaller space.
This makes collisions between the particles more frequent.
How does increasing the surface area increase the rate of reaction?
If one if the reactants is a solid then breaking it up into smaller pieces will increase the surface area to volume ratio.
This means for the same volume of a solid the particles around it have more area to work on so there will be collisions more frequently.
How do catalysts increase the rate of reaction?
A catalyst is a substance that speeds up a reaction without being used up in the reaction itself. This means its not part of the overall reaction.
Different catalysts are needed for different reactions but they decrease the activation energy.
How can you measure the rate of reaction from precipitation and colour change? (Practical)
You can measure the colour change if the initial solution is transparant and the product is a precipitate which clouds the solution.
Yoy can observe a mark through the solution and measure how long it takes for it to disappear.- the faster the mark disappears the quicker the reaction.
If the reactants are coloured and the products are colourless you can time how long it takes for the solution to lose or gain its colour.
How can you measure he rate of reaction through a change in mass?
Measuring the speed of a reaction that produces a gas can be carried out using a mass balance.
As the gas is released to mass disappearing is measured on the balance.
The quicker the reading on the balance drops the faster the reaction.
Take measurements at regular intervals.
This is the most accurate out the methods because the mass balance is very accurate.
How can you measure the rate of reaction by the volume of gas given off?
You would use a gas syringe to measure the volume of gas given off.
The more gas given off during a given time interval the faster the reaction.
It would be accurate and take measurements at regular intervals.
If the reaction is too vigorous it could blow the plunger out the end of the syringe.
How can you investigate the rate of reaction between magnesium and hydrochloric acid to produce hydrogen gas?
Start by adding a set volume of dilute hydrochloric acid to a conical flask.
Add magnesium ribbon to the acid and quickly attach a empty gas stringe to the flask.
Start the stop watch and read the volume of gas in the gas syringe at regular intervals.
Plot the results in a table.
