10.1 Reaction Rates

Question 1

What is meant by rate of reaction?

Answer 1

Rate of reaction measures how fast a reactant is being used up or product being formed.

The rate of a reaction can be defined as a change in concentration of a reactant or a product in a given time

Question 2

What factors affect the rate of reaction?

Answer 2

• concentration
• temperature
• Use of catalyst
• Surface area of a solid reactants
• pressure of gases

Question 3

What is the collision theory?

Answer 3

states that two reacting particles must collide at the correct orientation and correct energy for a reaction to occur. Only a small proportion of molecules result in a chemical reaction- they collide then bounce off each other and remain chemically unchanged in most reactions

Question 4

What are the 2 conditions that determines if a reaction will be ineffective?

Answer 4

• the particles would collide with the correct orientation

- Particles will have sufficient energy to overcome the activation energy barrier of the reaction.

Question 5

How does increasing the concentration affect the rate of reaction?

Answer 5

• increasing the concentration, the rate of reactant increases
• Increase in concentration increases the number of reactant particles in the same volume
• the particles are close together and collide more frequently
• In a given period of time there will be more frequent effective collisions at the correct orientation and sufficient energy and an increased rate of reaction

Question 6

How does increasing the pressure of gas affect the rate of reaction?

Answer 6

• increasing the concentration, the rate of reactant increases
• Increase in concentration increases the number of reactant particles in the same volume
• the particles are close together and collide more frequently
• In a given period of time there will be more frequent effective collisions at the correct orientation and sufficient energy and an increased rate of reaction

Question 7

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

Answer 7

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

• monitoring the removal (decrease in concentration) of a reactant
• Following the formation (increase in concentration) of a product

What reactions that produce gases?

• monitoring the volume gas produced at regular time intervals, using gas collection
• Monitoring the loss of mass of reactants using a balance
• Both are proportional to the change in concentration of a reactant or a product
• Therefore change in volume/change in mass give a measure of rate of reaction.

Question 8

What is the formula for reaction rates?

Answer 8

Amount of reactant used or product formed/ time

Question 9

How can we work out the rate of reaction?

Answer 9

Rate of reaction= amount of reactant used or product formed/ time

Change in mass= when the product is a gas its formation can be measured using a mass balance. The amount of product formed is the mass disappearing from the container
We use a regular stop clock and take mass measurements at regular time intervals
We know when the reaction is finished as the mass stops decreasing
This method is very accurate and easy to use but releases gas into a room that can potentially be dangerous- we can use a fume cupboard

We can also monitor the rate of reaction by observing how long it takes for a cross to be obscured on a paper (reduce errors)

Volume of gas given off-

• You can use a gas syringe to measure the volume of product formed
• You can measure the volume of gas in the syringe
• The method is accurate but vigorous reactions can blow the plunger out of the syringe

Gradient= change in y/ change in x