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Rates of Reaction 1
The smallest amount of energy required by particles to react is called the activation energy.

Rates of Reaction 1

Many factors affect rates of chemical reactions - pressure of gases, temperature, surface area of solids, concentration and if there is a catalyst. Anything that will change the probability of particles colliding or change the energy of the collisions will affect the rate of a reaction. This is the first of three GCSE Chemistry quizzes looking at these factors.

The rate of a reaction is a measure of how quickly a chemical reaction progresses. Some reactions can be very slow, for example rusting can take weeks or even years, whilst others, such as neutralisation or an explosion are over very rapidly. The rate of reaction is very important in industrial situations; take explosions for instance - these are incredibly fast reactions. An explosive is a solid that turns into a huge amount of very hot gas VERY quickly! This makes them useful for several purposes - most notably in warfare - though a more peaceful use is in the quarrying for resources.

1 .
Chemical reactions can only occur when...
particles come together with sufficient energy
particles come together for a sufficient amount of time
particles mix together
particles are able to separate
The amount of energy required is called the activation energy
2 .
The smallest amount of energy required by particles to react is called...
chemical energy
reaction energy
enabling energy
activation energy
If particles collide with less than the activation energy, a reaction will not take place
3 .
In order to accelerate the rate of a chemical reaction, there are two things which we can do. Pick the correct combination.
Decrease the chances of particle collision
Increase the energy the particles collide with
Increase the chances of particle collision
Increase the energy the particles collide with
Increase the chances of particle collision
Decrease the energy the particles collide with
Decrease the chances of particle collision
Decrease the energy the particles collide with
Particles will only react if they collide with each other so increasing the chances of collisions will increase the chances of a reaction occuring. Increasing the energy of collisions gives a better chance that they will collide with an energy greater than the activation energy
4 .
Which of the following is NOT a factor that affects the rate of a chemical reaction?
Temperature
Concentration
Surface area
The speed at which the chemicals are mixed
For a slow reaction, even if the chemicals are mixed instantaneously, it will still be a slow reaction and vice-versa
5 .
Which piece of laboratory equipment would be useful for measuring the volume of gas given off?
Beaker
Gas syringe
Conical flask
Burette
This would be the most convenient and accurate method of measuring the volume of gas given off, although theoretically you could use any of the other pieces of equipment
6 .
If 80 cm3 of gas was given off in a reaction in 20 seconds, what was the average rate of reaction?
4 cm/s
4 cm3/s
1,600 cm3/s
0.25 cm3/s
Rate of reaction = amount of reactant used up (or amount of product formed) divided by the time taken
7 .
One method of increasing the chances of particles colliding during a reaction between gases is to...
increase pressure
decrease temperature
use a catalyst
decrease concentration
Increasing pressure needs the gas mixture to be compressed. If it is compressed, the particles will be closer together and therefore more likely to collide
8 .
One method of increasing the energy the particles react with is to...
increase pressure
increase temperature
use a catalyst
decrease concentration
Increasing the temperature requires an input of heat energy which makes the particles move around faster, collisions will therfore involve higher energies
9 .
Which of the following methods is NOT a valid way to measure the rate of a chemical reaction?
Measuring the mass of a reaction mixture
Measuring the volume of gas given off
Measuring the light transmitted through a solution
Measuring the volume of liquid at the start of the reaction
If you just measured the volume of a liquid at the start, it tells you nothing about how fast the reaction happened after that point in time. Any method of measuring the rate of reaction MUST be measurable during the whole time of the reaction
10 .
A catalyst is...
a substance that slows down a chemical reaction, and is used up in the reaction
a substance that speeds up a chemical reaction, and is used up in the reaction
a substance that speeds up a chemical reaction, but is not used up in the reaction
a substance that slows down a chemical reaction, but is not used up in the reaction
Make sure that you know this definition off by heart for your GCSE
You can find more about this topic by visiting BBC Bitesize - Rates of reaction

Author:  Kate Gardiner

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