6. The Rate And Extent Of Chemical Change Flashcards
(23 cards)
How do you calculate the rate of reaction? (2 ways)
Mass of reactant/ time
OR
Volume of product formed/ time
What happens to the rate of reaction when temperature increases?
The rate if reaction increases due to more kinetic energy had by the particles, until the temperature is too high so the amount of energy results in the breaking of molecules
What happens to the rate of reaction if you increase the number of particles?
The rate of reaction increases because there are more particles that the particles can react and collide with.
What is the term for the number of particles in a gas?
Pressure
What is the term for the number of particles in a solid?
Surface area
What is the term for the number of particles in a liquid?
Concentration
What does a catalyst do?
A catalyst provides an alternative energy pathway which has a lower activation energy. This increases the rate of reaction. They are not used up in a reaction and are usually transition metals.
What needs to happen for a reaction to occur?
- particles need to collide
- particles need to collide in the right orientation
- particles need to collide with enough energy
What happens to the rate of reaction if the surface area is larger?
The rate of reaction increases as there are more locations for the reaction to take place
What happens to the rate of reaction in a large cube?
- there is a low surface area to volume ratio
- there are fewer places for the reaction to occur
- less frequent collisions
- low rate of reaction
What happens to the rate of reaction in a fine ‘dusty’ substance?
- There is a high surface area to volume ratio
- there are more places for the reaction to occur
- more frequent collisions
- high rate of reaction
What is a reversible reaction?
One in which the products of a reaction can react with each other to reform the original reactants.
When does an equilibrium occur?
When the rate of the forwards reaction is equal to the rate of the backwards reaction within a closed system. It will appear as though no reaction is occurring.
How does the position of the equilibrium change?
The position can change depending on the conditions (cooling/ heating). If you heat the reactant it will shift right as it is making more product (the forwards reaction is occurring more often) but if you cool the reactant, it will shift right as it is making less product (the backwards reaction is occurring more often.
What is Le Chatelier’s principle?
When a change is imposed on a system at equilibrium, the equilibrium will shift to counteract the change. Whatever you do the equilibrium it will either do more of reaction 1 (shift right) or more of reaction 2 (shift left)
What type of reaction is it if the temperature change is negative?
The forwards reaction is exothermic, the backwards reaction is endothermic.
What type of reaction is it if the temperature change is positive?
The forwards reaction is endothermic, the backwards reaction is exothermic
What does pressure depend on?
The number of particles within a volume.
What is activation energy?
The minimum energy needed for a reaction to be successful
How do you measure temperature change?
Use a thermometer to measure the change over time
How do you measure the gas given off?
Measure volume of gas emitted over time (water trough and measuring cylinder)
How do you measure precipitate formed?
Measure time taken for liquid to become opaque
How does concentration affect equilibrium?
If the concentration of one side (reactants or products) is increased it will try to remove extra concentration by performing the reaction the increased concentration is in more often
