Rates of reaction Flashcards
meaning of ‘rate of a chemical reaction’
Rate of reaction = time reaction takes to
speed at which reactants are converted into products in a chemical reaction.
List the factors that can increase the rate of a chemical reaction
- Temperature (done)
- Surface area
- Concentration of reactants
- Use of a catalyst/enzyme
Explain the function of a catalyst.
= chemical that speeds up a chemical reaction.
At the end of the reaction the catalyst is unchanged.
E.g. Enzymes
- A catalyst increases collision frequency by providing a surface and offers a lower energy pathway, resulting in more successful collisions and a faster reaction rate.
why does temp effect rate of reaction
In a COLD reaction particles move slowly,
- collisions are less frequent
- have less energy so there are fewer successful collisions
If we HEAT the reaction the particles move more QUICKLY,
- collisions are more FREQUENT with more energy so there are
- more SUCCSEFUL collisions.
why does increased concentration increase the rate of reaction?
At a higher concentration, there are more particles in the same amount of space.
This means that the particles are more likely to collide and therefore more likely to react.
Slower and slower!
Reactions start off at a certain speed, then get slower and slower until they stop BECAUSE the concentration of reactants decreases (as they are used up).
Why does surface area effect Rate
If the solid is split into several pieces, the surface area increases.
This means that there is an increased area for the reactant particles to collide with.
Increased surface area exposes more reactant particles, enhancing collision frequency and reaction rate.
Eg. Powdered sugar dissolves faster than a sugar cube.
example of catalyst
Many catalysts are transition metals or their compounds.
Eg.
- Nickel
- Iron
- Platinum
