topic 9 - separate chemistry 2

flame test - flame colour of a potassium ion (K+)

flame test - flame colour of a potassium ion (K+)

lilac

flame test - flame colour of a sodium ion (Na+)

yellow

flame test - flame colour of a lithium ion (Li+)

red

describe the test to identify halide ions

1. add dilute nitric acid to unknown solution

2. add silver nitrate to unknown solution

3. observe precipitate colour produced

results for test to identify halide ions (Cl-, Br-, I-)

• chloride ion (Cl-) = white precipitate

• bromide ion (Br-) = cream precipitate

• iodide ion (I-) = yellow precipitate

describe the test to identify carbonate ions

1. add dilute hydrochloric acid

2. observe whether bubbling occurs

results for test to identify carbonate ions

if bubbling occurs, carbonate ions are present

explain why the results of a test for presence of specific ions must be unique

in order to identify the specific ion without uncertainty

what is the precipitation colour of an aluminium ion (Al3+)

white (dissolves and goes colourless when excess NaOH is added)

describe the test to identify ions in solids or solutions using sodium hydroxide solution (NaOH)

1. add NaOH solution to unknown solution

2. observe the precipitate colour produced

3. if a white precipitate is formed add excess NaOH solution

flame test - flame colour of a copper ion (Cu2+)

blue-green

flame test - flame colour of a calcium ion (Ca2+)

brick red (orange-red)

precipitate test - precipitate colour of a iron 2 ion (Fe2+)

green

precipitate test - precipitate colour of a copper ion (Cu2+)

blue

precipitate test - precipitate colour of a calcium ion (Ca2+)

white

precipitate test - precipitate colour of a ammonium ion (NH4+)

white

precipitate test - precipitate colour of a iron 3 ion (Fe3+)

brown

describe the test to identify sulfate ions

• add dilute hydrochloric acid to unknown solution

• add barium chloride to unknown solution

• observe whether a white precipitate is formed

results for test to identify sulfate ions

if a white precipitate is formed, sulfate ions are present

describe the flame test to identify ions in solids

1. dip flame test loop into dilute hydrochloric acid

2. hold flame test loop in flame and then dip in beaker of water

3. dip clean flame test loop into one of the four known solids

4. observe and record the flame colour produced

describe the test for hydrogen gas

place a lighted splint in a test tube containing the gas. if the gas is hydrogen it will produce a squeaky pop

describe the test for oxygen

place a glowing splint in a test tube containing the gas. if oxygen is present the splint will relight

describe the test for carbon dioxide

bubble the unknown solution through limewater. if carbon dioxide is present, a white precipitate of calcium carbonate will be formed

describe the test for ammonia gas

dip a glass rod in concentrated hydrochloric acid and put this in the unknown gas. if ammonia is present, a white smoke of ammonium chloride will form

describe the test for chlorine gas

place a damp piece of litmus paper above a test tube containing the unknown gas. if the litmus paper is bleached, chlorine is present

what are the advantages of instrumental methods of analysis

• they are readily available

• can improve sensitivity of test

• can improve accuracy of test

• can improve speed of test

explain how to determine the concentration of ions in a dilute solution using a calibration curve

1. plot a calibration graph using concentration data points and flame photometer readings

2. y-axis is flame photometer readings

3. x-axis is concentration of ions

4. draw a horizontal line to the calibration curve from the chosen point on the y-axis

5. from the point the horizontal line connects to the curve, draw a vertical line down to the x-axis

6. work out the concentration of ions based on where the vertical line touches the x-axis

explain how to identify metal ions by comparing data with reference flame photometer data

• use a flame photometer to split the coloured light from a vaporised sample into an emission spectrum

• compare this spectrum to the reference flame photometry spectrum

• identify the metal ion from the reference spectrum

recall the molecular formulae of methane

CH₄

recall the molecular formulae of ethane

C₂H₆

recall the molecular formulae of propane

C₃H₈

recall the molecular formulae of butane

C₄H₁₀

recall the displayed structure of methane

recall the displayed structure of ethane

recall the displayed structure of propane

recall the displayed structure of butane

explain why alkanes are saturated hydrocarbons

• compound that contains ONLY carbon and hydrogen atoms

• and contains only single bonds

• between carbon atoms

recall the molecular formulae of ethene

C₂H₄

recall the molecular formulae of propene

C₃H₆

recall the molecular formulae of butene

C₄H₈

recall the displayed structure of ethene

recall the displayed structure of propene

recall the displayed structure of but-1-ene

recall the displayed structure of but-2-ene

explain why alkenes are unsaturated hydrocarbons

• compound that contains ONLY hydrogen and carbon atoms

• and contains at least 1 double bond between carbon atoms

recall what occurs in the addition reaction between ethene and bromine

• ethene + bromine → 1, 2-dibromoethane

• double bond between carbon atoms in ethene breaks

• to connect to the 2 bromine atoms

explain how bromine water can be used to determine between alkanes and alkenes

• alkanes - the orange bromine water will remain orange

• alkenes - the orange bromine water will become colourless

• because if an unsaturated compound is shaken with the bromine water, an addition reaction will occur

• causing the orange solution to turn colourless

state what the complete combustion of alkanes/alkenes involves

• involves oxidation of hydrocarbons

• to produce carbon dioxide

• and water

state what a polymer is

• substance of high average relative molecular mass

• consisting of small repeating units

explain how ethene molecules combine together in a polymerisation reaction

• one of the bonds in the carbon double bond in ethene breaks

• this allows the ethene monomer to bond to other ethene monomers

• they create a long, repeating chain of ethene monomers

• to create a poly(ethene) polymer

state what the product of the polymerisation of ethene is

poly(ethene)

explain the polymerisation reaction of atoms to create poly(propene)

• one of the bonds in the double bond between carbon atoms in propene breaks

• this allows the propene monomer to bond to other propene monomers

• they create a long, repeating chains of propene monomers

• called a poly(propene) polymer

state what the product of the polymerisation of propene is

poly(propene)

explain the polymerisation reaction of compounds to create poly(chloroethene)

• one of the bonds in the double bond between the carbon atoms in ethene breaks

• this allows the carbon atoms in ethene to bond to the one chloride atom

• this creates chloroethene

• chloroethene monomers bond together

• to create long, repeating chain of chloroethene

• called poly(chloroethene)

explain the polymerisation reaction of compounds to create poly(tetrafluoroethene)

• one of the bonds in the double bond between the carbon atoms in ethene breaks

• this allows the carbon atoms in ethene to bond to the four fluorene atoms

• creating tetrafluoroethene

• tetrafluoroethene monomers bond together

• to create a long, repeating chain of tetrafluoroethene

• called poly(tetrafluoroethene)

explain how to deduce the structure of a monomer from the structure of an addition polymer

• identify the repeating unit in the polymer

• change the single bond between carbon atoms in the repeating unit

• to a double bond in the monomer

• remove the bond from each end of the repeat unit and the subscript n

explain how the use of poly(ethene) in carrier bags is related to its properties

• thin

• cheap

• can be made into thin film

explain how the use of poly(ethene) in food wrap is related to its properties

• can be made into thin film

• cheap

• flexible

explain how the use of poly(ethene) in shampoo bottles is related to its properties

cheap

explain how the use of poly(propene) in buckets is related to its properties

• strong

• resists shattering

explain how the use of poly(propene) in bowls is related to its properties

• strong

• resists shattering

explain how the use of poly(propene) in crates is related to its properties

• strong

• resists shattering

explain how the use of poly(propene) in ropes is related to its properties

• flexible

• strong

explain how the use of poly(chloroethene) in insulation for electrical wires is related to its properties

• electrical insulator

• flexible

explain how the use of poly(chloroethene) in windows is related to its properties

tough

explain how the use of poly(chloroethene) in gutters is related to its properties

tough

explain how the use of poly(chloroethene) in pipes is related to its properties

• tough

• hard

explain how the use of poly(tetrafluoroethene) in non-stick coatings for pans is related to its properties

• slippery

• chemically unreactive

explain how the use of poly(tetrafluoroethene) in containers for laboratory substances is related to its properties

chemically unreactive

explain what a condensation polymer is

• formed when two different monomers are linked together

• with the removal of a small molecule

• usually water

state what an ester link is

• a link formed by a condensation reaction

• between an alcohol

• and a carboxylic acid

explain why polyesters are condensation polymers

• polyester is formed when a monomer molecule containing 2 carboxylic acid groups

• is reacted with a monomer molecule containing 2 alcohol groups

• one molecule of water is formed every time an ester link is formed

explain why the availability of starting material is an issue associated with polymers

• there is a low availability of starting material

• making the creation of polymers a longer and more expensive process

explain why the persistence of polymers in landfill sites is an issue associated with them

• polymers are non-biodegradable

• meaning when they are placed in landfill sites, they will not be broken down by microorganisms

• causing polymers to remain in landfill sites for long periods of time

• and waste space in landfill sites

explain why gases produced during disposal by combustion is an issue associated with polymers

• when polymers are burnt, carbon dioxide is produced

• carbon dioxide has a negative effect on the environment as it enhances the greenhouse effect

• in enclosed spaces, carbon monoxide can also be produced

• which can suffocate humans as it deprives the body of oxygen

explain why the requirement of sorting polymers for recycling is an issue associated with polymers

• separating different polymers is difficult

• and expensive

state the advantages of recycling polymers

• polymers are finite resources, meaning recycling prolongs their supply

• reduces the amount of non-biodegradable polymers ending up in landfill

• reduces the amount of crude oil needed as crude oil is the raw material needed to make new polymers

• prevents disposal of polymers by combustion, reducing the amount of carbon dioxide emissions produced

re

state the disadvantages of recycling polymers

• recycling polymers is difficult

• recycling polymers is expensive

• recycling process is energy-intensive which can contribute to climate change

• recycled polymers requires melting, which can produce toxic gases harmful to animals and plants

• recycling runs the risk of mixing different polymers together, which can alter the properties of the polymers

recall what DNA is

• a polymer

• made from four different monomers

• called nucleotides

recall what starch is

• a polymer

• based on sugars

recall what proteins are

• polymers

• based on amino acids

state the molecular formulae of ethanol

CH₃CH₂OH

state the molecular formulae of methanol

CH₃OH

state the molecular formulae of propan-1-ol

CH₃CH₂CH₂OH

state the molecular formulae of butan-1-ol

CH₃CH₂CH₂CH₂OH

recall the displayed structure of methanol

recall the displayed structure of ethanol

recall the displayed structure of propan-1-ol

recall the displayed structure of butan-1-ol

state what the functional group in alcohol is

-OH

state what is produced when alcohols are dehydrated

alkanes

state the method of how to investigate the temperature rise in a known mass of water by the combustion of alcohols

• set up a simple combustion calorimeter including a draught shield, insulating lid, thermometer and spirit burner

• use a measuring cylinder to measure 100cm³ of water into a copper can

• record the initial temperature of the water and the mass of the empty burner

• fill the spirit burner with ethanol and record its new mass

• place the spirit burner under the copper can, light the wick and place the insulating lid on

• stir the water constantly with the thermometer

• continue heating until the temperature rises by 25 degrees C

• immediately extinguish the flame and record the final mass of the spirit burner

• repeat these steps with propanol, butanol and pentanol, making sure to keep the volume of water and the distance between the wick and the bottom of the stand the same

state the molecular formulae of methanoic acid

HCOOH

state the molecular formulae of ethanoic acid

CH₃COOH

state the molecular formulae of propanoic acid

CH₃CH₂COOH

state the molecular formulae of butanoic acid

CH₃CH₂CH₂COOH

recall the displayed structure of methanoic acid

recall the displayed structure of ethanoic acid

recall the displayed structure of propanoic acid

recall the displayed structure of butanoic acid