C8: Rates of Reaction Flashcards
Average Rate of Reaction=
Amount of reactant used or amount of product formed / Time
4 factors that affect the Rate of Reaction
Temperature
Surface Area
Concentration of solutions/ Pressure of gases
Presence of a catalyst
What is Collision Theory?
An explanation of chemical reactions in terms of reacting particles colliding with sufficient energy for a reaction to take place.
What is Activation Energy?
The minimum energy needed for a reaction to take place.
2 factors that make a reaction more likely to occur?
> Increasing the frequency of particle’s collisions.
Increasing the kinetic energy of particles when they contain when they collide.
What effect does a larger Surface Area have on the rate of reaction?
It does not result in collisions with more energy, but it does increase the frequency of collisions as more particles are accessible to collide.
How does raising the temperature affect the rate of reaction?
Rate of reaction increases.
Why does heating a substance increase its rate of reaction?
> When a substance is heated, energy is transferred to its particles.
This means that the particles move around faster and have more kinetic energy causing them, to collide more frequently.
This gives them more chances to react.
(THIS FACTOR IS LESS IMPORTANT THAN THE FACT THAT THE COLLISIONS CONTAIN MORE ENERGY)
How does heating a substance affect a particle’s energy?
> Because the particles are moving faster, they have more energy.
This results in a higher proportion of particles having greater energy than activation energy.
This effects the rate of reaction.
What is the consequence of increasing the concentration of reactants in a solution?
It increases the rate of reaction because there are more particles of the reactants, making the collisions more frequent.
What is not affected by an increase in the pressure or concentration of a substance?
The energy with which particles collide. It only affects the frequency of collisions.
What is the consequence of increasing the pressure of reacting gases?
Gas particles are squashed closer together, which increases the chance and therefore frequency of collisions and reactions.
What is a Catalyst?
A substance that increases the rate of reaction and is not changed or used up in the reaction.
What can we do to make catalysts as effective as possible?
Increase their Surface Area
Positives of using catalysts.
> They don’t get used up- only a small amount is needed.
They’re good for the environment (don’t burn as many fossil fuels).
Often cheaper than paying for extra energy.
