Unit 3 Flashcards
What are industrial processes designed to maximise and minimise
Maximise profits and minimise the impact on the environment
7 factors that influence the design of an industrial process
availability, sustainability, cost of feedstock, opportunities for recycling, energy requirements, marketability of by-products and product yield.
environmental considerations of chemical processes
minimising water, avoiding use or production of toxic substances, designing products which will biodegrade if appropriate.
molar volume is the same for…
ALL gases at the same temperature and pressure
what is the approximate molar gas volume
22.4 litres mol -1
what are the units used for molar volume
litres mol -1 NOT to be confused with moles per litre
what are the units for concentration
mol l-1
Define the term ‘dynamic equilibrium’
Many reactions are reversible. A reversible reaction can meet equilibrium in a closed system.
When does equilibrium occur
When the rate of the forward reaction is equal to the rate of the backward reaction.
What happens to concentrations at equilibrium
They stay constant
State Le Chatelier’s principle
An equilibrium will move to undo any change imposed upon it by temporarily favouring either the forward or backward reaction until a new equilibrium position is reached.
In increase in pressure favours the side with…
Less Gas particles
Addition of a reagent or removal of a product moves the equilibrium to the
right
Addition of a product or removal of a reagant moves the equilibrium to the
left
Increase in temperature favours the
endothermic reaction
Decrease in temperature favours the
exothermic reaction
State the effect a catalyst has on equilibrium
A catalyst has no effect on the equilibrium position but will help to reach equilibrium faster
State the pressure, temperature and other conditions applied to the haber process
High pressure (balanced by cost of equipment), moderately high temperature (lower temperature improves yield but reaction is then too slow). Unreacted products are recycled, an iron catalyst is used to speed up the reaction.
State the definition of percentage yield
The percentage yield is a measure of how much product is obtained compared to the amount expected if there was a complete conversion.
State the definition of atom economy
The atom economy measures the proportion of the total mass of all the starting materials successfully converted into the desired product.
Explain why there can be a high percentage yield but a low atom economy.
Means a lot of waste products are being produced.
What is Enthalpy
Enthalpy (H) is a measure of the energy stored in a chemical.
State the definition of the enthalpy of combustion
The enthalpy of combustion of a substance is the amount of energy given out when one mole of a substance burns in excess oxygen.
State Hess’ law
The overall enthalpy change for a reaction is the same whichever route is taken.
What is meant by molar bond enphalpy
The energy required to break one mole of bonds.
What is an oxidising agent
The substance that gains electrons. In theory, it is being reduced and so become more negative.
What is a reducing agent
The substance that loses electrons. In theory, it is being oxidised and so becomes more positive.
Are metals reducing or oxidizing agents.
They tend to lose electrons and so are reducing agents.
Which group in the periodic table contains the strongest reducing agents?
The alkali metals
Which group in the periodic table contains the strongest oxidising agents.
Halogens
Where are the strongest oxidising and reducing agents on the electrochemical series.
Oxidising agents - Bottom left hand corner
Reducing agents - Top right hand corner
Are acidified dichromate and permanganate oxidising or reducing agents?
They are oxidising agents
Examples of uses of oxidising agents?
Water purifier, Bleach
List the steps in writing an ion-electron half equation
Balance the unusual atoms first.
Balance the oxygens by adding water.
Balance the hydrogens by adding H+ ions
Balance the charge by adding electrons to the more positive side.
State the basic principles of how chromatography works
Chromatography separates compounds according to their relative affinity for the mobile phase and the stationary phase
What can be in the mobile phase
Liquid or gas
What can be in the stationary phase
Silica, gel, or an inert packing material
What is the formula for Rf
distance travelled by sample / distance travelled by solvent
What is the Rf
Retention factor
State the principle of volumetric analysis using titration
Volumetric analysis involves using a solution of known concentration to determine the amount of another substance present. The volume of the reactant needed to complete the reaction is determined by titration.
What is an indicator in titration and give two examples
A substance that changes colour in response to a chemical change.
Phenolphalein - pink to colourless
Permanganate self indicating - purple to colourless
What is the ‘end point’ of a titration reaction
The term the ‘end point’ is where the indicator changes colour and means that the solutions have been mixed in exactly the right proportion according to the equation.
What is a standard solution
A solution of accurately known concentration
How do you create a standard solution
Dissolve the calculated mass of solid in the minimum volume of water in a beaker. Transfer to the standard flask and then dilute up to the graduated mark on the standard flask.
Explain the relative accuracy of a range of volumetric measuring equipment.
Burette and pipette allow the volume to be measured accurately.
Error may occur in the judging of the endpoint/colour change.
