C5.2
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What is rate of reaction
A measure of how quickly reactants are used up or products formed.
Two formulas for rate of reaction
rate of reaction = amount of reactant used/time taken Rate of reaction = amount of product formed/time taken
What should u measure to work out rate of reaction if a gas is produced
You should measure the volume of the gas as it’s easier than measuring the mass. You can do this by using an upturned cylinder or a gas syringe.
How can you calculate instantaneous rate of reaction
By working out the gradient of the graph
How can you calculate mean rate of reaction
By using the total time and total mass/volume
What are the conditions needed for a reaction to happen
The reactant particles need to collide with each other The colliding particles have enough energy to react
What is a successful collision
A collision that leads to a reaction occurring
What happens to rate of reaction as temperature increases
As the temperature of a reaction mixture increases, the particles move quicker, so they collide more often, a greater proportion of the particles have the activation energy or more. The greater the rate of successful collisions, the greater the rate of reaction.
What is the formula for rate of reaction in terms of reaction time
1/reaction time = rate of reaction
What happens to rate of reaction at higher concentrations
As concentration increases rate of reaction increases. This is because the particles become more crowded, so they collide more often. The energy doesn’t change but because the number of collisions increases, the rate of successful collisions increases.
Why do reactions go faster at higher pressures
If a gas is involved in a reaction the rate of reaction increases as the pressure of the gas increases. The particles in the gas state become more crowded as they collide more often. The rate of successful collisions increases.
What happens to particles in the solid state
The particles in the solid state can only vibrate in fixed positions. They can’t move from place to place. This means that only the particles at the surface can take part in collisions.
What happens as the surface area increases
More reactant particles are available for collisions Collisions are more likely, so particles collide more often This leads to an increase in the rate of reaction.
At which points are surface areas increasing
As the size of the lumps decreases, the surface area to volume ratio increases.
What is a catalyst
A catalyst is a substance that increases the rate of reaction but is unchanged at the end of the reaction. Catalysts are specific to particular reactions.
What are enzymes
Enzymes are biological catalysts.
How do catalysts work
Catalysts work by providing an alternative reaction pathway with a lower activation energy . A greater proportion of the colliding particles have activation energy or more . The rate of successful collisions increases compared to the rate in an un-catalysed reactions