Revision topic 9 Flashcards
to work out the rate of chemical reaction we have to measure
how quickly the reactants are used up to make the products, or how quickly the products of the reaction are made
set up a method to see the effect of surface area on a reaction
Equipment:
Marble chips in 3 sizes Dilute hydrochloric acid 25ml measuring cylinder Plastic/metal spatula 100ml conical flask Cotton wool Stopwatch or timer Balance to 2decimal places
Method
Measure out 20ml of hydrochloric acid and add to the conical flask, don’t forget the cotton wool
Place on the balance and record the mass
Take 1 piece or one spatula of the marble chips and put into the conical flask.
Quickly replace the cotton wool and start the timer
Record the change in mass after 3 minutes.
Repeat the experiment for other size marble chips.
we can conclude that having a higher surface area would lead to a faster reaction time
set up a method to see the effect of catalysts on the reaction time
Equipment:
Magnesium ribbon cut into 1cm strips Hydrochloric acid 25ml measuring cylinder 100ml conical flask with bung & delivery tube Gas syringe Stopwatch or timer catalysis
Method
Measure out 20ml hydrochloric acid and add to the conical flask.
Set up the equipment as shown in the diagram.
Take 1 piece of magnesium and catalyst remove the bung and put it into the conical flask.
Quickly replace the bung and start the timer
Record how long it takes the bubbles to stop appearing.
Repeat the experiment without the catalyst
we can conclude from this that having a catalyst increases the reaction time
set up a method to see the effect of acid temperature on the reaction time
Equipment: Sodium thiosulphate Dilute (0.25M) hydrochloric acid: 1x room temp 1x ice bath 1x ~50ᵒC water bath 2x 25ml measuring cylinder 100ml conical flask White paper with a black cross drawn on Stopwatch or timer
Method
Measure out 20ml of sodium thiosulphate and add to the conical flask.
Set up the equipment as shown in the diagram.
Measure out 20ml of acid from the ice bath and add to the conical flask. Start the timer
Record how long it takes for the cross to no longer be visible through the mixture.
Repeat the experiment for the room temperature and warm acid.
we conclude from this that the warmer the acid the faster the reaction time
rate of reaction =
amount of reactant used or amount of product formed over time
what are the 4 main factors that affect the rate of reaction
- temperature
- surface area
- concentration
- presence of a catalysts
what is collision theory
it is a theory which states that particles must collide with a certain minimum amount of energy before they react
what is the activation energy
is the minimum amount of energy that particles must have before they react
how are reactions most likely going to happen between reactant particles
by increasing their frequency or by increasing the energy they have when they collide
if you increase the surface area of reactants particles
you increase the frequency of their collisions
why does increasing the rate of temperature increase the rate of reaction
because by increasing the rate of temperature you would increase the energy and frequency at collision
why does increasing the temperature lead to more frequent collisions and more energy
because if you heat up a substance the energy from the heat would be transferred to their particles making them move faster and collide more, this would give the higher portion of particles energy greater than the activation energy making the reaction take place
how does increasing the concentration or presure increase the rate of reaction
when you increase the concentration you would have more particles in the same volume so this would lead to more frequent collisions resulting in a faster reaction time, the same idea can be applied to increasing the pressure of the gas, cause if you increase the pressure of gas the particles would become closer to each other resulting in more collisions giving us a faster reaction time
set up a method to see the effect of concentration on a reaction
Equipment:
Marble chip Hydrochloric acid: 0.25M, 0.5M, and 1M. 25ml measuring cylinder Plastic/metal spatula 100ml conical flask Cotton wool Stopwatch or timer Balance to 2 decimal places
Method
Measure out 20ml of 1M hydrochloric acid and add to the conical flask, don’t forget the cotton wool
Place on the balance and record the mass
Take 1 piece or one spatula of the marble chips and put it into the conical flask.
Quickly replace the cotton wool and start the timer
Record the change in mass after 3 minutes.
Repeat the experiment for other concentrations of acid.
we can conclude that having a higher surface area would lead to a faster reaction time
what are catalysts
they are substances that would increase the rate of reaction without changing the reaction chemically, they are not used up in the reaction so they can be used over and over again they usually come in forms of powders, pallets, and fine gauzes this gives them a bigger surface area and makes them more effective over time
