C5 Flashcards
(26 cards)
Concentration =
Concentration=Mass/ volume (dm3)
Explain how to carry out a titration
1) Add a set volume of your acid/ alkali to a conical flask
2) add a few drops of inductor
3) fill a burette with the alkali/ acid
4) add slowly while swirling the glass until it changes colour
5) measure the amount of acid/ alkali used to neutralise
What volume does one mole of gas occupy at room temperature and pressure?
one mole of gas occupies 24dm3 at room temperature and pressure
Volume of a gas=
Volume of a gas= moles x 24
What is a percentage yield
A percentage yield is the percentage of products you get from a reaction
Percentage yield =
Percentage =. actual yield. X 100
Yield ——————
Theoretical yield
Why do we not always get 100% percentage yield? (Three reasons)
We don’t always get 100% percentage yield because some products is lost when being separated from the reaction mixture, some reactants may react unexpectedly and some reversible reactions may not go to completion
What is atom economy?
Atom economy is the percentage of the mass of reactants converted to desired products
Atom economy =
Atom economy= mr of desired products/ mr of all products x100.
Reaction rate=
Amount of reactant used or product formed / time
The collision theory definition
Particles can only react when they collide with sufficient energy. The rate of a chemical reaction depends on the frequency of successful collisions
How does increasing the temperature increase reaction rate?
Increasing the temperature increases the energy of the particles which means they move faster so the frequency of collisions increases. Each collision also has more energy so they are more likely to overcome the activation energy and collide successfully and react.
How does increasing concentration/ gas pressure effect reaction rate
Increasing concentration/ gas pressure increased the number of particles which means they’re more likely to collide which increases the frequency of collisions and thus the reaction rate
How does increasing the surface area effect reaction rate
A smaller object has a larger SA:V ratio compared to a larger object which means there are more particles on the surface of a smaller object able to collide with so there are more collisions per second which increases the reaction rate
Explain how to do a experiment to investigate the effect of temperature and concentration on reaction rates
(Hint- precipitation)
1) use any two reactants that will produce a precipitate eg sodium thiosulfate +hydrochloride acid —> sulfur
2) place in a conical flask placed over a black printed cross
3) start the stopwatch and swirl the mixture until you can no longer see the cross then stop the stopwatch
4) repeat using different temperatures of concentrations
Explain an experiment to investigate the effect of surface are on reaction rates
(Hint- hydrogens gas)
1) use any two reactants that will produce a gas
2) set up a conical flask containing hydrochloric acid, attach a bung, delivery tube and gas syringe
3) add a large chunk of marble chip into the acid and start the stopwatch
4) record the gas volume in the syringe every 30s for five minutes
5) repeat using he same mass of marble chips in smaller pieces
Definition of a catalyst
Catalyst- a substance which increases the rate of a reaction without being used up in the reaction
How to catalysts work?
Catalyst work by decreasing the activation energy of a reaction by providing an alternative pathway with a lower activation energy
Give the name of a biological catalyst and what it does
Enzymes are biological catalysts which speed up chemical reactions in living cells such respiration, protein synthesis and photo synthesis
What is a reversible reaction.
A reversible reaction is a reaction in which the reactants make the products and the products make the reactants
What is dynamic equilibrium?
Dynamic equilibrium is where both reaction are still happening but there is not effect because the concentrations have reached a balance and won’t change
Where can dynamic equilibrium only take place?
Dynamics equilibrium can only take place in a closed system
What is le Charteliers principle?
Le charteliers principle states that if we change the conditions of a reversible reaction the position of equilibrium will shift to oppose the change
How would changing the temperature of a reversible reaction effect the position of equilibrium
All reactions are exothermic in one direction and endothermic in the other. If the temperature were to increase equilibrium would move towards the endothermic direction to absorb the extra heat
If the temperature was to decrease equilibrium would move towards the exothermic direction to produce more heat
