Rates & Energy Flashcards
How can the rate of a reaction be found?
Measuring how much of a reactant is used
How much of a product is formed in the time taken
Which 2 equations can calculate ROR?
Amount of reactant used/ time OR amount of product formed/ time
What does the rate of reaction measure?
The speed of a reaction or how fast it is.
How can you calculate the ROR from a graph?
Find the gradient at any given point; the steeper the gradient, the faster the reaction
A reaction can only occur if …..?
Particles collide
What is the activation energy?
The minimum energy that substances need to react
What factors will increase the rate of reaction?
Factors which will increase the chance of collisions or increase the energy of the particles
List the 5 factors that increase the ROR
Temperature Concentration of solutions Pressure of gases Surface area of solids Using a catalyst
Why do powders react faster than solid large pieces?
Powders have a larger surface area so more of the surface is exposed to react and means there is more collisions in the same time so the powder reacts much faster
Why does a higher temperature mean a faster reaction?
Increasing the temperature increases the speed of the particles in a reaction meaning they collide more often and a larger proportion will collide with greater energy than the activation energy which increases the rate of reaction
By how much will the rate of reaction increase if the temperature is increased by 10 degrees?
Double the rate of reaction ps, twice as fast
Why do freezer foods sty fresher for longer?
The decrease in temperature will increase the time that it takes for the reactions within the food to take place; decrease of 10 degrees reaction is twice as slow
Why does a higher concentration increase the ROR?
A higher concentration means there are more particles dissolved in the same solution so the particles are closer together so will collide more frequently and more collisions go to succession
Why does increasing the pressure increase the ROR?
Increasing the pressure puts more molecules in the same volume and so they collide more frequently this increases the ROR
How do catalysts speed up the ROR?
They lower the activation energy.
Why can catalysts be used again and again?
It is not used up so can be collected at the end of a reaction and reused
Why do different reactions need different catalysts?
Catalysts often work with only one type of reaction
What are the benefits of using catalysts in industrial processes?
The reduce the energy needed and the time needed and so reduce costs they may also reduce the fossil fuels need so conserves resources and reduces pollution
What is bad about using transition metal catalysts?
Some of these metals and their compounds are toxic and may cause harm if the enter the environment
What 2 areas of science offer possibilities for new or better catalysts?
Nanoscience and enzymes
What is an exoteric reaction?
Reactions that transfer energy to the surroundings
Exoteric reactions include:
Combustion, burning fuels
Oxidation, respiration
Neutralisation, reactions involving acids and bases
What is an endothermic reaction?
Reactions that take energy in from the surroundings
What usually happens in an exoteric reaction?
The temperature increases
What are the 2 ways that show a reaction is endothermic?
Either it cools the surroundings or it needs to be heated to keep it going
Give an example of an endothermic reaction and what makes it endothermic?
Thermal decomposition as it must be heated to keep the reaction going
In reversible reactions the forward and reverse reactions involve ……… But ………. Energy transfers
Equal
Opposite
A reversible reaction that is ……. In one direction must be …………. In another direction
Exothermic
Endothermic
Why must blue copper sulphate be heated continuously to change it into anhydrous copper sulphate?
Endothermic reaction
Why does adding water to anhydrous copper sulphate cause the mixture to get hot?
The reaction is exothermic
Give an ad and a disad of a re-usable hand warmer compared with a single use hand warmer
Ad: less waste, less materials or resources used
Disad: has to be heated so it can be used again, slower reaction smaller temp rise
Suggest an ad and disad of a chemical cold pack compared with an ice pack
Ads: can be used anywhere, can be stored easily,
Disad: only be used once, more waste, more possibly hazardous
