Chemistry unit 5+6 Flashcards
(29 cards)
Formula for rate of reaction
Amount of reactant used/ time or amount of product formed/time
How do we measure the quanitity of the mass and product
In g of cm^3 or in moles
How is rate measured
In g/s or cm^3/s or in mol/s
How to find rate of reaction from a graph
Draw a tangent at the point on the curve and draw a triangle and then use the equation to work out gradient
Factors affecting rate of chemical reactions
Concentration
Pressure
Surface area
Temperature
Catalysts
Defined collision theory
Chemical reactions can only occur only when reacting particles collide with each other and with sufficient energy
What is activation energy
The minimum amount of energy needed that particles must have to react
Explain how temperature increases reaction rate
Higher temperatures = more energy so more frequent collisions leading to quicker reaction
Explain how concentration affects rate of reaction
More particles in as smaller area means more frequent collisions so more particles reach activation energy and a quicker rate of reaction
What is a catalyst
A substance that can provide an alternate pathway for a reaction in order to decrease activation energy so more particles get the activation energy necessary and increase rate of reaction without being used up
What is a reversible reaction
When the products of the reaction react to make the reactants. We use the reversible reactions arrow to show this
Energy changes in reversible reactions
A reversible reaction being exothermic one way is endothermic the other way
What three things need to go on a reaction profile graph
Overall energy change
Activation energy
Reactant and products
What is an exothermic reaction
A reaction where bonds are built up and and energy is released to its surroundings
What is an endothermic reaction
A reaction where bonds are broken down and energy is absorbed through into its surroundings.
What do we call the reactions plus products
The system (the surroundings are everything else)
What does an exothermic reaction profile show us
More energy is released when new bonds are formed then the energy absorbed when bonds pare broken
What does an endothermic reaction profile show us
More energy is absorbed to break the bonds than the energy released when building the bonds
What are the uses of an exothermic reaction
Hand-warmers that are both single use and reusable by making it with materials that form a reversible reaction, self heating cans that use calcium oxide
What are the uses of endothermic reactions
Ice packs with ammonium nitrate that numb pain, keeping drink containers to keep them cool
What is a bond energy calculation
The calculation that shows the change in energy from reactions to products
What is dynamic equilibrium
When the rate of the forward and reverse reactions are equal, the system is at dynamic equilibrium. The reaction is constantly moving making it dynamic
What is le chatiliers principle
If conditions in the system are changed, the reaction will try to oppose change to restore the dynamic equilibrium
What happens when a reaction at dynamic equilibrium increases in concentration of reactants
More product gets produced the balance the equilibrium’s
