C2.4

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How can you measure the rate of reaction?
By measuring how much reactant is used, how much product is formed (the gas released), the time taken and the gradient of a graph.
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What are the equations for the rates of reaction?
Amount of reactant used ÷ time. Amount of product formed ÷ time
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What does the collision theory state?
That reactions can only happen if particles collide with enough energy; activation energy – minimum energy to react.
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What can increase the chance of collisions/energy of particles to increase the rate of reaction?
Temperature, concentration of solutions, pressure of gases, surface area of solids (powder) + catalyst.
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Why is the rate of reaction faster with powder than with larger pieces of solid?
Increasing the SA = more frequent collisions and so the rate of reaction is faster.
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How does increasing the temperature increase the rate of reaction?
As the particles collide more often with more energy increasing the rate of reaction.
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How can increasing the concentration or pressure increase the rate of reaction?
As increasing the concentration of reactants in solutions and pressure of reacting gases increases the frequency of collisions between particles.
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How can a catalyst speed up the rate of reaction?
By lowering the activation energy of the reaction do that more of the collisions result in a reaction, but different reactions often need different catalysts and have a large SA for maximum efficacy.
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What are the advantages of using catalysts?
Economical as: they don’t need to be replaced often, reduce time and energy (reducing impact on environment + saving money)
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What are the disadvantages of catalysts?
Many involve transition & their compounds, many of which are toxic and can; if exposed, harm the environment + some are expensive.
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What two areas of research offer possibilities for new or better catalysts?
Naniparticles (large SA) and enzymes which are biological catalysts that work at ordinary temperatures. Both can reduce energy + costs even further if they replace trad. Catalysts
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What are exothermic reactions?
Reactions that transfer energy to the surroundings, often heating up the surroundings and so increasing in temperature.
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Give examples of exothermic reactions.
Combustion (i.e. burning fuels), oxidation reactions (respiration) + neutralisation reactions (involving acids + bases) –Handwarmer.
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What are endothermic reactions?
Reactions that take energy from the surroundings. Some cause a decrease in temperature + others require a supply of energy.
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Suggest examples of endothermic reactions.
Thermal decomposition reactions need to be heated continuously – happen as the solid compounds dissolve in water – chemical icepacks forsport
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What do reversible reactions involve?
Equal but opposite energy transfers. It is exothermic in one direction + endothermic in the other direction
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Card 2

Front

What are the equations for the rates of reaction?

Back

Amount of reactant used ÷ time. Amount of product formed ÷ time

Card 3

Front

What does the collision theory state?

Back

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Card 4

Front

What can increase the chance of collisions/energy of particles to increase the rate of reaction?

Back

Preview of the front of card 4

Card 5

Front

Why is the rate of reaction faster with powder than with larger pieces of solid?

Back

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