Extra Flashcards
Explain why adding a catalyst to the reaction mixture without changing any other conditions can cause a rate of the reaction to increase?
A catalyst decreases the activation energy
State two properties of the collisions between particles that affect the rate of the reaction
The frequency of the collisions
Energy of the colliding particles
What does increasing the volume of the vessel do?
Decreases the pressure
State whether the reaction equation will change if cerium oxide is present in the reaction vessel explain your answer?
No, it won’t because it isn’t used up in the reaction so doesn’t appear in the equation because it is a catalyst
Suggest how you would check whether the results are repeatable?
Repeat the experiments with the same method and compare the results to check that they are similar
Describe and explain with reference to collision theory how the rate of reaction changes during it?
Rate decreases as the amount of reactant fours so does the concentration so the frequency of collisions between the reactant particles decreases
What is equilibrium?
The rate of the forward reaction is equal to the rate of the backward reaction
The forward reaction is endothermic, which two things can you say about the enthalpy change for the reverse reaction?
It is exothermic, so the same amount of energy will be reversed in the reverse reaction has taken in the forward reaction
Suggest to changes that could be made to the mixture so that it would change its colour?
Changing the temperature
changing the concentration
Tip: when there are colours within a reaction, reactants colours, can you mix to create another colour
What do you do when you sketch the reverse reaction?
Swap round the reactants to the graphs so they are the opposite way
What happens when something reaches equilibrium?
When equilibrium is reached the amount of each substance, stop changing and so does the colour
Compare the viscosity of petrol and diesel?
diesel will be more viscous because it has a higher boiling point meaning that is a longer chain and larger molecules
Predictor of a petrol or diesel will be more flammable. Explain why?
Petrol has a lower boiling point, meaning it contains smaller molecules in smaller chains so is more flammable
Fractions boil over a range of temperatures, much narrower than the original crude oil. What does this suggest about the structures of hydrocarbons in a fraction?
Similar number of carbon atoms similar chain length
Suggest two types of useful materials produced from crude oil fractions
Solvent, lubricant, polymers, and detergent
What type of reaction is cracking?
Thermal decomposition/endothermic
Describe how cracking is carried out?
Hydrocarbons are vaporise the vapour is then passed through a hot catalyst, all mixed with steam, and then heated to very high temperatures
What uses are there for alkenes from cracking?
Polymers and starting materials for other chemicals
Explain why and house in fractions of crude or a process for cracking giving chemical equations were relevant?
There’s a high demand for shorter chains because they make good fuel
Longer chains are less useful so less demand
Cracking helps supply short chains
Long chains are heated and vaporised
Vapour passes over a hot catalyst or is mixed with steam to a very high temperature so it’s thermally decomposes
It is useful for fuels and alkanes are used for starting materials for compounds and polymers
When writing, incomplete combustion, what should you do?
Only include the products carbon dioxide, carbon monoxide and water
Explain why the bunk is an important safety precaution when using a Bunsen burner to heat a boiling tube
Hydrocarbons are very flammable. The bong prevents the hydrocarbon vapour from escaping and igniting.
One of the students had a lot more gas in the test to then the others at the end of the experiment suggest an error that occurred
They didn’t fully fail, the test tube of water at the start
Suggest what is important to remove the apparatus from the water when water is sucked back up for the delivery to
Because the hot boiling tube Can crack
Suggest why it would not be possible to carry out this experiment in a lab without a catalyst
It wouldn’t be hot enough and would not be safe to reach the temperature needed so need a catalyst