[Part 2]- C8- the rate and extent of chemical change 💥 Flashcards
Describe how temperature, affects the rate of reaction ?
Hint: don’t explain
- when the temperature, it increases the rate of reaction
- ; when the temperature decreases, this decreases the rate of reaction.
Using collision theory, explain in detail how changing the temperature, alters the rate of reaction [6]
Hint: increase
- increasing the temperature, increasing the rate of a [chemical] reaction.
- This is because, an increase in temperature, increases the speed at which particles can move.
- This then increases the number of collisions that occur, as they now collide more frequently.
- and because the number of collisions occurring is increased, this increases the energy of the collisions.
- Increasing the energy of the collisions, increases the number of particles that now have energy greater than the activation energy, [because they have overcome the activation energy barrier]
- and because of this, this increases the chance of successful collisions [fruitful collisions]= which increases the rate of reaction.
In simple terms, explain why increasing the temperature, can affect rate of reaction [3]
- increasing the temperature, increases the speed of the particles.
- this is because, it increases the number of successful collisions, and the rate at which they collide, is now more frequent.
- therefore, this increases the rate of reaction
Fill in the gaps: Because the rate of ________ increases with temperature, the rate of _______ is ____________ to the temperature.
- Because the rate of reaction increases with temperature, the rate of reaction is proportional to the temperature.
In simple terms, explain why decreasing the temperature, can affect rate of reaction [4]
- decreasing the temperature, decreases the speed of the particles.
- this is because, it decreases the number of successful collisions, and the rate at which they collide, is now less frequent.
- since at a lower temperature, they move slower and don’t collide with each other frequently
- therefore, this decreases the rate of reaction
What’s concentration ?
Hint: dissolved in water
- concentration, is a measure of how much solute, is dissolved in a solvent [such as water]
Explain the effect of concentration [of reactants], on rate of reaction ? [3]
Hint: collision theory
- increasing the concentration of reactants in a solution, increases rate of reaction.
- This is because, increasing the concentration, means there’s more particles available to collide.
- This then means the collisions are more frequent, since this increases the frequency of having a [successful] collision- meaning this increases the rate of reaction.
- Fill in the gaps: Because the rate ________ if we increase the concentration, the rate is ____________ to the concentration.
Fill in the gaps: Because the rate increases if we increase the concentration, the rate is proportional to the concentration.
What’s pressure ?
Hint: the area on which it is exerted
- pressure, is the force exerted, divided by the area on which it is exerted.
- [and it’s usually measured in pascals (Pa) ]
Explain the effect of pressure [of reacting gases] on rate of reaction ?
Hint: collision theory
- increasing the pressure, increases rate of reaction.
- This is because, increasing the pressure, pushes and squashes the particles close together.
- This then increases the chance of having a [successful ] collision because, the collisions are more frequent [and therefore this also increases they chance they will react.]
- and this, increases rate of reaction.
Easy: how does changing concentration, affects the rate of reaction ?
- increasing concentration increases the rate of reaction.
- and decreasing concentration, decreases the rate of reaction
Easy: how does changing pressure affects the rate of reaction ?
- increasing pressure increases the rate of reaction.
- and decreasing pressure, decreases the rate of reaction
How can gas pressure, be changed ?
Hint: squeezing into a smaller volume
- pressure is affected by the number of molecules.
- the is because, the more molecules/ moles of a gas there are, the higher the pressure.
- therefore, gas pressure can be increased, by squeezing it’s given mass, into a smaller volume
Explain how changing pressure, has no effect on rate of reactions, for some reactions
- changing pressure has no effect on rate of reactions, for some reactions because:
- changing the pressure on a reaction which involves only solids or liquids has no effect on the rate. [as it doesn’t involve a reacting gases]
Why does pressure only involve reacting gases ?
- gas pressure only involves reacting gases because:
- gas pressure is caused by the force exerted by gas molecules, colliding with the surfaces of objects
- gases are compressible, unlike liquids or solids
What’s a catalyst ?
Hint: remains chemically unchanged
- a catalyst, is a substance that increases [speeds up] the rate of chemical reactions; it remains chemically unchanged itself, at the end of the reaction.
How do catalysts work ?
- catalysts provide an alternative reaction route, and this alternative reaction route has a lower activation energy.
Explain the effects of a catalyst, on rate of reaction [3]
Hint: higher proportion
- catalysts provide an alternative reaction route which has a lower activation energy.
- this means, the particles require less energy, to cross the activation energy barrier
- and because the particles require less energy to cross the activation barrier, the a higher proportion of the reactant particles, have energy to react.
- meaning, the frequency of effective and successful collisions increases, therefore rate of reaction increases.
- Fill in the gaps: the rate of ________, depends on the number of _________ that have energy to cross the activation barrier, and _______ successfully
- the rate of reaction, depends on the number of particles that have energy to cross the activation barrier, and collide successfully
What’s three important things, you can tell me about catalysts ?
- we don’t include catalysts in the chemical equation, for a reaction.
- different reactions, need different catalysts
- and, enzymes act as catalysts in living organisms
Why don’t we include catalysts, in the chemical equation, for a reaction ?
- we don’t include catalysts, in the chemical equation, for a reaction because:
- catalysts remain chemically unchanged at the end of a reaction [they’re not used up in the reaction]
- and, catalysts are not a reactant.
Describe how adding a catalyst, affects rate of reaction ?
- adding a catalyst, increases the rate of [a chemical] reaction
Using an example, explain the industrial use of a catalyst
Hint: hardening vegetable oil
- For example, Nickel is a transition metal and catalyst, that is used to make margarine by hardening vegetable oil [through the process of hydrogenation]
What are some other examples, of industrial uses of catalysts ? [2]
Hint: ammonia, nitric acid
- iron, is used to make ammonia by the Haber Process
- platinum, is used in the manufacture of nitric acid [Ostwald process]
- [Easy] Fill in the gaps: Transition metals make ____ catalysts
- Transition metals make good catalysts
What are two reasons why catalysts are important ? [2]
Hint: quickly
- catalysts allow us to quickly carry out reactions, without need to increase the temperature- saving money
- catalysts remain chemically unchanged at the end of the reaction [not used up]- meaning, they can be be reused again and again.
Why are catalysts important ?
Hint: less energy
- catalysts are an important use in industry because, they allow reactions to happen at a lower temperature or lower pressure.
- this means, less energy is needed to drive the reaction.
