Reactions Flashcards
Does endothermic release or take in heat from the surroundings?
Takes in heat
Does exothermic take in heat or give off heat to/from the surroundings
Gives off heat
Reaction profile diagram for exothermic explained:
More energy is stored in the bonds of the reactants than the products
Reaction profile for an endothermic reaction explained:
More energy is stored in the bonds of the products than the reactants
Examples off applications of an exothermic reaction
Combustion, respiration, metals and acids
Examples of applications of endothermic reactions:
Thermal decomposition, Photosynthesis
In an exothermic reaction will the temperature rise or not
Yes the temp of the reaction will go up
In an endothermic reaction will the temp go up or not
No temperature will decrease
What happens if you add a catalyst to the reaction
The catalyst will lower the activation energy in order to speed up the reaction
In an exothermic reaction are bonds made or broken
Made (MEXican)
In an endothermic reaction are bonds made or broken
Broken (BENdy)
What is the energy needed to break 1mole of a covalent bond in a molecule called
BOND ENERGY (kJ/mol)
How can we work out wether a reaction is endothermic or exothermic without measuring temp change
BENDY MEXICAN (calculating wether bonds are made or broken)
Method to calculate wether the reaction is endothermic or exothermic
- Calculate energy in (bonds broken)
- Calculate energy out (bonds made)
- Calculate the overall energy change (energy in - energy out)
- If the value is negative it is EXOTHERMIC and if the value is positive it is ENDOTHERMIC
What is needed for a reaction to happen
Reactant particles must collide with each other with a minimum of activation energy. Successful collisions have the activation energy or more
How does a change in temperature affect the rate of a reaction
Increases when temperature increases because particles gain energy and move faster.
Allows the frequency of collisions to increase and so a greater proportion of these are successful
How does the change in concentration and pressure affect the rate of a reaction
Increases if the concentration of a dissolved reactant increases OR if the pressure of a reacting gas increases
There are more particles in the same volume so the frequency of successful collisions increases
How does a change in surface area to volume ratio affect the rate of a reaction
Increases when the surface area:volume ratio of a solid reactant increases e.g. when lumps are made into powder
More particles of reactant are available so the frequency of successful conditions increases
What is a catalyst
A substance that speeds up the rate of reaction without being used up in the process or altering the products of the reaction
Give an example of a biological catalyst and what is it used for
Enzymes
Used in the production of alcoholic drinks
What does activation energy mean
The minimum amount of energy requires for a successful collision (reaction) to take place
