How Particle Size Affects Rate of Reaction
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How does one increase the surface area of a solid?
By dividing the solid into smaller pieces
What is increased when a solid is divided into smaller pieces?
The surface area of the solid
How does increased surface area affect rate of reaction?
The more surface area of the solid that is exposed to the reactants the faster a reaction will occur
How does increasing the surface area of a solid increase the rate of reaction between the solid and reactants?
As more of the solid is exposed to the reactants
What is an example of an experiment where increased surface area causes a faster rate of reaction?
The reaction of marble/calcium carbonate with dilute hydrochloric acid solution
Describe how the reaction between marble/calcium carbonate and dilute hydrochloric acid solution is carried out. 7 key steps
• 5g of powdered calcium carbonate is added to a conical flask • 50 cm cubed of hydrochloric acid solution is added to a graduated cylinder • The acid is poured into the conical flask containing the powdered calcium carbonate where it is swirled • A cotton wool plug is immediately added to the mouth of the conical flask and a stopwatch is started • The mass of the calcium carbonate is recorded at 30 second intervals until the reaction has stopped and bubbles are no longer produced • Repeat the experiment using the same mass of marble chips • Note that the reaction using the powdered calcium carbonate will take less time to reach completion that the marble chips experiment
How much calcium carbonate is added to a conical flask?
5g
What two forms of calcium carbonate are used in this experiment?
Powdered calcium carbonate Marble chips
During the first step of this experiment where is the 5g of calcium carbonate added?
To a conical flask
What acid is used in this experiment?
Hydrochloric acid solution is used
How much Hydrochloric acid solution is used in this experiment?
50 cm cubed
In the second step of this experiment where is the 50 cm cubed of hydrochloric acid added?
A graduated cylinder
In the third step of this experiment what is added to the conical flask of calcium carbonate?
The 50 cm cubed of hydrochloric acid is added
What must immediately be done when the acid is added to the calcium carbonate?
A cotton wool plug must be placed in the neck of the conical flask The conical flask must be swirled A stopclock must be started
At what intervals is the mass of the calcium carbonate recorded after the addition of acid?
At thirty second intervals
Approximately how long will the experiment take?
10 minutes
When is it clear the reaction has been completed?
When bubbles are no longer formed
Why is a cotton wool plug used in this experiment?
The cotton allows for only the loss of carbon dioxide to affect the mass of the calcium carbonate
What does the cotton wool plug allow to escape from the conical flask?
It allows Carbon Dioxide to escape
What does the cotton wool plug not allow to escape from the conical flask?
It doesn’t allow acid spray formed as the marble reacts with the acid to escape
What is the main problem when dealing with finely divided particles?
Dust explosions
What type of particles cause a dust explosion?
Very small, energy-rich particles
Give an example of a substance which can cause a dangerous dust explosion
Coal dust in a mine
Give an example of a substance which can be used in a laboratory to create a controlled dust explosion
Lycopodium powder which is a type of very fine pollen