topic 5 - separate chemistry 1

state what most metals are known as

transition metals

state the properties of transition metals

• high melting/boiling point

• high density

• they form coloured compounds

• catalysts of metals and their compounds

state what the oxidation of iron causes

corrosion

state the definition of corrosion

• the gradual destruction of metal

• due to chemical reactions between metals, oxygen and water

explain how the exclusion of oxygen can prevent iron rusting

• rusting is the reaction of oxygen, water and metal together

• to form iron oxide

• without oxygen, this reaction cannot take place

explain how the exclusion of water can prevent iron rusting

• rusting is the reaction of oxygen, water and metal together

• to form iron oxide

• without water, this reaction cannot take place

explain how sacrificial protection can prevent iron rusting

• when iron is galvanised with a metal of a higher reactivity

• the iron is protected from water and oxygen by a physical barrier

• although reactions will take place with the galvanised metal, oxygen and water

• the iron will remain unreacted

state what electroplating is

• process where

• the surface of one metal

• is coated with the layer

• of a different metal

explain how electroplating can be used to improve the appearance of metal objects

• electroplating allows a metal object to be coated in a layer of another metal

• this coating could improve the appearance of the metal object

• e.g. silver plating cutlery and jewellery

explain how electroplating can be used to improve the resistance to corrosion of metal objects

• electroplating allows a metal object to be coated in a layer of another metal

• this coating is usually a metal with higher reactivity than the metal object

• this mean the metal coating will react with oxygen and water and corrode

• meaning the metal object is physically protected from the oxygen and water

state what a metal alloy is

• where metals are physically mixed together

• but not chemically combined

explain why converting metal into alloys increases the strength of the product

• alloys often have properties that differ to the pure metal

• alloys contain atoms of different sizes that disrupt the regular arrangement of atoms

• this makes it harder for the layers of metal atoms to slide over each other

• making the alloy harder than the pure metal

• thus making it stronger

explain why iron is alloyed with other metals to produce alloy steels

• cast iron from a furnace is 96% iron

• with carbon, phosphorus, silicon and sulfur impurities

• cast iron is too brittle for many common uses

• so it is alloyed to make steel by removing some of the impurities

• where it can then be used for actions such as construction, transport and manufacturing

explain how the uses of aluminium as foil is related to its properties

• used in domestic food wrapping/storing food

• as it has a low reactivity

• and is very malleable

state what the magnalium alloy is made of

• magnesium

• aluminium

explain how the uses of magnalium in aircraft parts is related to its properties

• magnalium is low density

• and corrosion resistant

• meaning it is a safe material to use in aircrafts

explain how the use of copper in electrical wirings is related to its properties

• copper is corrosion resistant

• and an electrical conductor

• making it a safe material to use in the wirings

state what brass is made of

• copper

• zinc

explain how the use of brass in pins for electrical plugs is related to its properties

• brass is stronger than copper

• and is also an electrical conductor

• making it a good material to use in the pins

state what jewellery gold is made of

• gold

• copper

explain how the use of jewellery gold in in jewellery is related to its properties

• the gold alloy allows the jewellery to stay strong

• whilst still remaining shiny

• and corrosion resistant

state the equation to find concentration in mol/dm³

concentration (mol/dm³) = no. of moles (mol) / volume (dm³)

state the equation to convert concentration in mol/dm³ to g/dm³

g/dm³ = mol/dm³ x M_r

state the equation to convert concentration in g/dm³ to mol/dm³

mol/dm³ = g/dm³ / M_r

state the method of how to carry out an acid-alkali titration

1. use pipette and pipette filler to place 25cm³ of NaOH solution into the conical flask

2. place the conical flask on a white tile so the tip of the burette is inside the flask

3. add a few drops of suitable indicator to the conical flask

4. perform a rough titration by taking an initial burette reading, while swirling the flask

5. quickly close the tap when a sharp colour change occurs and record the final volume at eye level

6. repeat the titration with a fresh flask of NaOH solution

7. at the rough end volume, add the solution from the burette one drop at a time until the indicator just changes colour

8. record the volume to the nearest 0.5cm³

9. repeat until 2 concordant results are achieved

explain how to use titration results to carry out simple calculations

1. write out the balanced reaction of the neutralisation reaction

2. calculate the moles of the known solution given the volume and concentration

3. use the equation to deduce the moles of the unknown solution

4. use the moles and the volume of the unknown solution to calculate the concentration

state the equation to find percentage yield

% yield = (actual yield / theoretical yield) x 100

state what actual yield is

• the yield of a reaction

• that is usually less than the calculated theoretical yield

state what causes the actual yield of a reaction to be less than the theoretical yield

• incomplete reactions

• practical losses during the experiment

• competing, unwanted reaction

state what atom economy is

• studies the amount of reactants that get turned into useful products

• it’s used to analyse the efficiency of reactions

state the equation to find atom economy

atom economy = (M_r of desired products / M_r of all reactants) x 100

explain why a particular pathway in a reaction is chosen to produce a specified product using atom economy

• reactions that have low atom economies use up a lot of resources

• and produce excess waste material

• which needs to be disposed of

• making it an expensive procedure

• these reactions are unsustainable as they aren’t economically attractive

explain why a particular pathway in a reaction is chosen to produce a specified product using yield

• high yield rates are desirable attributes of chemical reactions

• as they produce less waste products

• therefore improving the efficiency of the reaction

• making the reaction more economically-attractive

explain why a particular pathway in a reaction is chosen to produce a specified product using equilibrium position

in reversible reactions, the position of equilibrium may need to be changed in favour of the products by altering reaction conditions

explain why a particular pathway in a reaction is chosen to produce a specified product using usefulness of by-products

• if by-products can be sold or reused that would improve the atom economy of a reaction, making it a more economical pathway

• alternative methods of production could also be considered that may produce a more useful by-product

state what the molar volume of any gas at room temperature and pressure is

• the volume occupied by one mole of molecules of any gas

• at room temperature and pressure

state the molar volume of any gas at room temperature and pressure

24 dm³

state the molar volume equation

vol (dm³) = mol x molar volume (dm³/mol)

state Avogadro’s Law

• at room temperature (20°C) and pressure (1 atmosphere)

• one mole of any gas

• has a volume of 24dm³

state what type of reaction the Haber process is

• reversible reaction

• between nitrogen and hydrogen

• to form ammonia

predict how the rate of attainment of equilibrium is affected by changes in temperature

• higher temperature

• means the particles have more kinetic energy

predict how the rate of attainment of equilibrium is affected by changes in pressure

• higher pressure

• means the frequency of successful collisions between particles

• will increase

predict how the rate of attainment of equilibrium is affected by changes in concentration

• higher concentration

• means more particles per given volume

• increasing the frequency of successful collisions between particles

predict how the rate of attainment of equilibrium is affected by the presence of a catalyst

• lowers activation energy

• allowing a reaction to reach equilibrium faster

explain how conditions in industrial reactions are related to the availability and cost of raw materials and energy supplies

• if the cost of extraction of raw materials is too high or they are unavailable, then the process is no longer economically viable

• many industrial processes require huge amounts of heat and pressure which is very expensive to maintain

• production energy costs are also a factor to be considered carefully and alongside the raw materials issue

explain how conditions in industrial reactions are related to the control of temperature is used to produce an acceptable yield in an acceptable time

• a higher temperature would favour the reverse reaction as it is endothermic so a higher yield of reactants would be made

• a lower temperature would favour the forward reaction as it is exothermic so a higher yield of products will be made

  • however, at a lower temperature, the rate of reaction is very slow

  • so a COMPROMISE TEMPERATURE between having a lower yield of products but them being made quicker must be found

explain how conditions in industrial reactions are related to the control of pressure is used to produce an acceptable yield in an acceptable time

• lower pressure would favour the reverse reaction as the system will try to increase the pressure by creating more molecules so a higher yield of reactants will be made

• higher pressure would favour the forward reaction as it will try to decrease the pressure by creating fewer molecules so a higher yield of products will be made

  • however high pressures can be dangerous and very expensive equipment is needed

  • so a COMPROMISE PRESSURE must be found between a lower yield of products that are made safely and economically

explain how conditions in industrial reactions are related to the control of a catalyst is used to produce an acceptable yield in an acceptable time

• presence of a catalyst DOESN’T affect the position of equilibrium

• but it DOES increase the rate at which the equilibrium is reached

• because the catalyst increases the rate of both the forward and reverse reactions by the same amount

• thus, the concentration of reactants and products is the same at equilibrium as it would be without the catalyst

• so the use of a catalyst allows for an acceptable yield to be achieved at a lower temperature by lowering the activation energy required

describe the Haber Process

• hydrogen and nitrogen react

• to form ammonia

• in a reversible reaction:

• N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

describe the formation of ammonia in the Haber Process

• formation of ammonia is exothermic

• formation of nitrogen and hydrogen is endothermic

predict the ideal conditions for the Haber Process

• as the formation of ammonia is exothermic

• Le Chatelier’s Principle would predict that:

• reaction will produce a higher yield at a lower temperature

• and using a higher pressure would increase the yield

• as there are fewer moles of gas on the right than on the left of the equation

state the ideal conditions of the Haber Process

• temperature - 450ºC

• pressure - 200 atmospheres

• catalyst presence - yes

state what fertilisers contain to promote plant growth

• nitrogen

• phosphorus

• potassium

state the reaction of ammonia to produce a fertiliser

• ammonia + nitric acid → ammonium nitrate

• NH₃ (aq) + HNO₃ (aq) → NH₄NO₃ (aq)

describe the method of the laboratory preparation of ammonium sulfate

1. add ammonia solution and a few drops of methyl orange to a conical flask using a pipette

2. add dilute sulfuric acid to the burette using a measuring cylinder and note the starting volume

3. add the sulfuric acid to the conical flask slowing until the methyl orange changes colour

4. calculate the volume of acid added and repeat the titration without indicator

5. transfer the solution to an evaporating basin and heat to partially evaporate water

6. remove the evaporating basin from heat and allow filtrate

7. after a few days ammonium sulfate crystals will appear

8. filter to remove any remaining water

9. this is a SMALL SCALE OPERATION

describe the industrial preparation of ammonium sulfate

• LARGE SCALE OPERATION

• ammonia is prepared by Haber Process and sulfuric acid by the Contact Process

• most common industrial process involves filling a large reactor chamber with ammonia gas

• sulfuric acid is sprayed into the chamber from above and ammonium sulfate powder is produced

compare the laboratory preparation and industrial production of ammonium sulfate (EQUIPMENT)

• LAB:

  • simple equipment needed

  • prepared using a titration apparatus

• INDUSTRIAL:

  • hugely expensive and complex

compare the laboratory preparation and industrial production of ammonium sulfate (REACTANT CONCENTRATION)

• LAB:

  • low concentrations

  • less heat given off

• INDUSTRIAL:

  • high concentrations

  • exothermic reaction

compare the laboratory preparation and industrial production of ammonium sulfate (SEPARATION OF PRODUCT)

• LAB:

  • crystallisation is used which is a slow process

• INDUSTRIAL:

  • heat produced is used to evaporate water from the reaction mixture

  • this makes a very concentrated ammonium nitrate product

state what a chemical cell does

• produces a voltage

• until one of the reactants is used up

describe the reaction inside a fuel cell

• hydrogen and oxygen are used

• to produce a voltage

• and water is the only product

state the strengths of fuel cells

• do not produce any pollution

• produces more energy per kilogram than petrol or diesel

• no power is lost in transmission

• no batteries to dispose of - better for the environment

• quieter - less noise pollution

state the weakness of fuel cells

• materials used in producing fuel cells are expensive

• high pressure tanks are needed to store sufficient hydrogen and oxygen - dangerous and difficult to handle

• become less efficient in low temperature

• hydrogen is expensive to produce and store