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RATES OF REACTION (Reversible reactions (We can change the rate by…
RATES OF REACTION
Reversible reactions
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If it is exothermic in one direction, it is endothermic in the other
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Mean rate of reaction
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In a graph:
Steep slope=faster rate
Becoming less steep=shows us the rate is slowing down
Flat line= all of the reactants have been used up
Using tangents
The slope is constantly changing, which means that the rate is constantly changing. This is overcome by drawing straight lines called tangents.
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Effect of concentration
Collision theory - chemical reactions can only take place when reacting particles collide, and have enough energy. The rate of reaction is determined by frequency of collisions.
Rate increases with concentration, so it is PROPORTIONAL
Effect of surface area
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With 2 blocks, there is a greater surface area so there are more collisions. This means that the rate of reaction increases with surface area, so these are also PROPORTIONAL.
Effects of temperature
When a product has less energy than what it started with, it means this reaction is exothermic. The energy increases before the reaction completes and this is called the ACTIVATION ENERGY.
Temperature increase gives particles energy, causing more collisions. This means that the rate of reaction increases with temperature.
Catalysts
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Increase the rate by providing different pathways, lowering the activation energy
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