GCSE Topic 7 - Rate of reaction Flashcards
What are the pieces of information that required to calculate the rate of reaction?
- Time
- Amount of reactant used or product produced
List the factors that affect the rate of a reaction
- Catalyst
- Temperature
- Surface Area
- Concentration (solutions)
- Pressure (gases)
Define a catalyst
A substance that speeds up the rate of a reaction by lowering the activation energy. It is not used up in the reaction.
What are units for volume?
cm3
Define an enzyme
A biological catalyst
State some uses of enzymes
- Making ethanol in alcohol drinks
- Detergents
- Forensic analysis
What group of elements are often catalysts?
Transition metals
Desribe how a catalyst works
- Reactant molecules adsorb onto the surface, forming temporary bonds with the catalyst.
- Bonds within the molecules weaken and then break.
- Atoms of the reactant molecules are rearranged to form the product molecules.
- Product molecules desorb from the surface.
What is the symbol equation for magnesium reacting with hydrochloric acid?
Mg (s) + 2 HCl (aq) ⇒ MgCl2 (aq) + H2 (g)
What is the symbol equation for marble chips reacting with hydrochloric acid?
CaCO3 (s) + 2 HCl (aq) ⇒ CaCl2 (aq) + H2O (l) + CO2 (g)
Explain why increasing temperature increases rate of reaction
- Reactant particles have more kintetic energy
- There is a greater proportion of reactant particles that have above the activation energy
- There are more frequent and successful collisions between reacant particles
Explain why increasing concentration increases rate of reaction
- There are more reactant particles per unit volume
- There are more frequent and successful collisions
Explain why increasing pressure increases rate of reaction
- There are more reactant gas particles per unit volume
- There are more frequent and successful collisions
Explain why there is a greater of rate of reaction with powdered solids
- There is a greater surface area
- There are more exposed reactant particles
- There are more frequent anf successful colliisions
Define an endothermic reaction
- A reaction where heat energy is taken in (specification)
- A reaction where there is an energy change from thermal to chemical
- There is a decrease in temperature
Define an exothermic reaction
- A reaction where heat energy is given out (specification)
- A reaction where there is an energy change from chemical to thermal
- There is an increase in temperature
What is the energy change with a salt dissolving in water?
Endothermic
What is the energy change with a neutralisation reaction?
Exothermic
What is the energy change with a displacement reaction?
Exothermic
What is the energy change with a precipitation reaction?
Either exothermic or endothermic
Is bond breaking endothermic or exothermic?
Endothermic
Is bond making endothermic or exothermic?
Exothermic
Explain in terms of bonds why a reaction is exothermic
More energy is released in making bonds than is used to break bonds
Explain in terms of bonds why a reaction is endothermic
More energy is used to break bonds than is released in making bonds
How is the energy change of reaction calculated using bond energies?
(Total bond energies of reactants) - (total bond energies of products)
Define the term ‘activation energy’
The minimum energy needed to start a reaction
What is the formula for calculating the rate of a reaction?
Rate = amount of product produced / time
How can you tell from a graph when a reaction has stopped?
When the graph just starts to flatten
Explain why the rate of reaction decreases as a reaction progresses
There are fewer reactant particles per unit volume
Explain how the shape of a graph can be used to compare rates of reaction
The steeper the gradient, the higher the rate of reaction
