Reaction Rates

Question 1

What is the rate of a reaction?

Answer 1

The change in the concentration of a reaction or product in a given time.
—> How fast a reactant is used up/ how fast a product is formed.

Question 2

Describe and explain how concentration of reactants changes over time.

Answer 2

D - The curve is the steepest at the start of the reaction when the rate is the greatest.
—> E - The reactants have the greatest concentration - the rate of reaction is the fastest.
D - The curve becomes less steep as the reaction proceeds.
—> E - The concentration of the reactants decreases - the rate of reaction slows down.
D - The curve becomes a straight line when the reaction is complete.
—> E - One of the reactants has been used up do the rate of reaction is 0.

Question 3

Which factors affect the rate of reaction?

Answer 3

• Temperature
• Pressure
• Concentration
• Surface Area
• Catalysts

Question 4

What is collision theory?

Answer 4

For a reaction to be successful, particles must collide in the correct orientation with energy which is greater than the activation energy.

Question 5

How does concentration effect the reaction rate?

Answer 5

• If the concentration of the reactants increase, then the number of collisions increase.
• The proportion of molecules with energy greater than the activation energy remains the same.
• The frequency of successful collisions increases.
• Therefore, the rate of reaction increases.

(Inverse for decreasing conc.)

Question 6

How does pressure effect the reaction rate?

Answer 6

• If the pressure increases, then the volume of the container has decreased., so, the number of collisions increases.
• The proportion of particles with energy greater that activation energy remains the same.
• The frequency of successful collisions increases.
• Therefore the rate of reaction increases.

(Inverse for decreasing pressure)

Question 7

What are the two methods for following the progress of a reaction?

Answer 7

1. Monitoring the removal of a reactant.
2. Monitoring the formation of a product.

Question 8

What are 2 ways of measuring the rate of reaction from a reaction which produces gases?

Answer 8

1. Monitoring the volume of gas produced at regular time intervals using gas collection, ie. A gas syringe.
2. Monitoring the loss of mass of reactants using a balance.

Question 9

• REQUIRED PRACTICAL -

Describe how you could monitor the production of gas using gas collection.

Answer 9

1. Set up a side-arm boiling tube connected to a gas syringe onto a clamp stand.
2. Measure a known volume of a concentrated acid and add to the side-arm boiling tube.
3. Place a piece of metal ribbon, of known mass, into the boiling tube and quickly put a stopper in place. Start the stop watch immediately.
4. Record the volume of gas in the gas syringe every 10 seconds until the volume stays the same/ the reaction is over.
5. Repeat the experiment with other concentrations of acid and represent your results on a graph of volume of gas produced against time.

Question 10

Describe how you would monitor the loss of reactants using a balance.

Answer 10

1. Add a carbonate and an acid to a conical flask placed on a balance.
2. Record the initial mass of the flask and record the mass at regular time intervals.
3. The reaction is complete when no more has is produced so, the mass no longer changes.
4. Plot a graph of mass lost against time.