Topic 7 Flashcards
rate of reaction equation
time
what is the precipitation practical for investigating rate of reaction
- mix two see through solutions to produce a precipitate which clouds the solution
- mix reactants and put the flask on a piece of paper with a cross on it
- observe mark through mixture and time how long it takes fir the mark to be obscured
- the faster it disappears the faster the reaction
- the result is subjective to view and agreement
what is the change in mass practical for investigating rate of reaction
- you can measure the rate of reaction that produces a gas using a mass balance
- as the gas is released the lost mass is easily measured on the balance
- the quicker the reading on the balance drops the faster the reaction
- you know the reaction has finished when the reading on the balance stops dropping
- use results to plot change in mass over time
- the method does release gas straight into room so it should be done in a fume cupboard
what is the practical with the volume of gas given off for investigating rate of reaction
- use gas syringe
- the more gas given off during 5 minutes the faster the reaction
- you can tell the reaction has finished when no more gas is produced
- use results to plot a graph of gas produced over time
- be careful to use correct syringe size otherwise vigorous reaction will blow plunger out the end of the syringe
how can you measure how surface area affects rate of reaction
- place 5g of marble chips in 40ml of dilute HCl in conical flask with bung and delivery tube to gas syringe
- measure volume of gas produced taking readings every 10 seconds for 2 minutes and put in table
- plot graph
- repeat experiment with same volume and con of acid and same mass of marble chips but use them more crushed up
- repeat with same but powdered chalk
- compare results
what do finer particles of solid mean
a higher rate
finer particles mean a larger surface area
greater mass also means more surface area and so faster reaction and more gas released
how can you measure how conc affects rate of reaction
- marble chips experiment but change conc of acid not chips
how can you investigate how temperature affects rate of reaction
- look at reaction between sodium thiosulfate and HCl
- both clear colourless solutions that react to form yellow precipitate
- use the amount of time that it takes for the coloured precipitate to form as a measure of rate
- measure out 50ml using measuring cylinder
- use water bath to heat both to 20 degrees
- mix in concial flask over black mark on paper and see how long it takes to disappear
- repeat at different temperatures
gradient
change in x
rate of reaction on graph is
the gradient of the line
what is collision theory
the rate of reaction depends on:
- the collision frequency of reacting particles, the more successful collisions there are the faster the reaction is
- the energy transferred during a collision. The minimum energy that the particles need to react when they collide is called the activation energy. Particles need to collide with at least the activation energy for the collision to be successful
why does breaking a solid reactant into smaller pieces increase the rate of reaction
it will increase the surface area to volume ratio so the particles around it will have more area to work on so the frequency of collisions will increase so rate of reaction will be faster
what are catalysts
- increases rate of reaction without been used up or changed
- won’t change products or reactants just make them quicker
- you only need tiny amounts because it isn’t used up
- they decrease the activation energy so more particles have the minimum amount of energy needed for a reaction to occur during a collision
what reactions are catalyzed by enzymes
respiration
photosynthesis
protein synthesis
what happens if the input energy is less than the activation energy
nothing because theres not enough energy to start
