C8- the rate and extent of chemical change 💥 Flashcards
What is the rate of a chemical reaction ?
- the rate of a chemical reaction, is the speed at which a chemical reaction takes place
How can the mean rate of reaction be calculated ?
Hint: quantity/time
- the mean rate of reaction can be calculated, by using equation=
- quantity of product formed ➗ time taken
In a reactant —> product graph, what does the slope of the line tell us ?
- if the quantity of product against time is plotted, the slope of the line gives us an idea of the rate of reaction.
- this is because, the sleeper the slope, the faster the reaction
In the reactant —> product graph, for the quantity of product formed against time, why does the graph get less steep ?
- ; the slope of the line will gradually become less steep- telling is rate of the reaction is decreasing [the reaction is slowing down.]
- this is because, a lot of the reactant molecules have already reacted, and turned into product- therefore, fewer reactant molecules are available to react.
In the reactant —> product graph, why is the slope of the line now zero, and the line is flat. [at the end]?
Hint: all the reactant molecules…
- at the end, the slope of the line is now zero, and the line is flat.
- this is because, at this point the reaction has stopped, since all of the reactant molecules have already reacted.
What are the units for the quantity of product formed ?
Hint: not a compound unit
- the quantity of product formed is typically in grams
- ; if our product is a gas, the quantity is then measured in cm^3
What does the reactant —> product graph, look like ?
- the rate is initially fast; the reaction then slows down and the reaction finally stops
Define the term ‘collision theory ?’
Hint: how chemical reactions…
- collision theory, is a scientific explanation of how chemical reactions occur.
- ; collision theory also explains how various factors, can affect the rates of reactions
Explain the concept of collision theory
Hint: reacting particles…
- collision theory states that: chemical reactions can only occur, when the reacting particles collide with each other.
- This is because, the collisions must have sufficient energy
- ; collision theory also states, the rate of a chemical reaction, is determined by the frequency of fruitful collisions [successful]
What do collision theory state, as the reason for a reaction between reactants ?
Hint: collisions
- collision theory states that the reaction between reactants, is due to: the collisions of the reactants particles, and the energy they have when they collide
According to collision theory, why don’t all collisions lead to a reaction ?
Hint: minimum energy
- not all collisions lead to a reaction because, they have a certain minimum energy known as the activation energy.
- Fill in the gaps: Any change in __________ that increase: the number of collisions and the ______ of the particles, will increase the ____ of reaction.
- Any change in conditions that increase: the number of collisions, and the number of the particles, will increase the rate of reaction.
Why are the five conditions [factors], that the rate of [chemical] reactions depend on ? [5]
Hint: catalyst
- temperature
- the concentration of liquids, and pressure of gases.
- the surface area of solid reactants
- and, the presence or absence of a catalyst
What does frequency mean ?
Hint: number
- frequency, is the number of successful collisions, per second
Explain the effect of surface area, on rate of reaction
Hint: collision theory
- collision theory states, that the reaction between reactants is due to: the collisions of the particles of the reactants, and the energy they have when they collide is needed
- so increasing the surface area, exposes more solid particles to the other reactant
- this then increases the frequency of successful collisions [of the reactants’ particles]- and therefore, the rate of reaction increases.
- This is because, if surface area increases—> more particles are available to react——> more successful collisions——> and the rate of reaction increases.
