Chemistry Paper 2

Give two conclusions you can make from Figure 5

• the flowers have no colours in common

• A / B contain one colour

• C contains two colours

• (the colour in) B is most soluble

Describe how oxides of nitrogen are produced when petrol is burned in car engines.

• nitrogen (from atmosphere) reacts with oxygen (from atmosphere)

• at high temperature (in engine)

HOW did the composition of the atomosphere change

• volcanic activity released water vapour

• the water vapour condensed to form oceans

• carbon dioxide dissolved in oceans

---

• algae and plants evolved / appeared

• algae / plants absorbed carbon dioxide

• by photosynthesis

• which also released oxygen

---

• carbon locked up in fossil fuels

Why are scientists not certain about the percentage of each gas in the Earth’s early atmosphere?

limited or no evidence as it was billions of years ago

what ion is to be present by the cream precipitate (when silver nitrate is added)

bromIDE (ignore bromine)b

describe the combustion of alkenes

they burn with smoky flames due to incomplete combustion

oxidation of the alcohols leads to ----

carboxilic acids

characteristsics of carboxilic acids

disolve in water to form an acidic solution

react with metal carbonates to form CO2

react with metals to give off hydrogen gas

react with alcohols to make esters, but onlu in the presence of an acid catalyst

amide bond

(C=O)NH2

what is an amino acid

(COOH)-NH2

reaction for the combustion of ethane in oxygen

2C2H6+7O2→4CO2+6H2O+Energy

describe how ethene forms polyethen

1. double bond breaks

2. many (ethene) molecules

3. bond together (join to form a long hydrocarbon)

Glucose is produced when algae photosynthesise.

Name two naturally occurring polymers produced from glucose

starch and cellulose

describe the shape and structure of this polymer

2 polymers wound together to form a double helix, with 4 nucleotides

Particles of soot in the atmosphere cause

global dimming

Titan is warmer than the other moons of Saturn because its atmosphere contains the greenhouse gas methane.

Explain how this greenhouse gas keeps Titan warmer than the other moons of Saturn

1. (methane) allows short(er) wavelength radiation to pass through (from the sun)

2. (which is) re-emitted from the surface as long(er) wavelength radiation

3. (which is) absorbed (by methane in the atmosphere)

Glass is made by heating sand with two other materials. Which two other materials are used to make glass?

limestone

sodium carbonate

Chlorine gas is used to produce poly(chloroethene). Describe a test to identify chlorine gas. Give the result of the test

(add damp) litmus paper

(litmus paper) is bleached or (litmus paper) turns white

what is a thermosetting polymer

is a polymer that is obtained by irreversibly hardening a soft solid or viscous liquid prepolymer

what is a thermosoftening polymer

Thermosoftening (also called thermoplastics) are plastics which will soften when heated and can be reshaped.

Poly(ethene) is a thermosoftening polymer. Suggest why poly(ethene) is easier to recycle than thermosetting polymers.

1. (poly(ethene)) melts

2. (so) can be reshaped (into new products)

What type of polymer is polymer A?

thermosetting

Why does polymer A behave differently to polymer B when heated?

polymer A has crosslinks (between polymer molecules) or polymer B has no crosslinks (between polymer molecules)

what does crosslinks mean

molecules r held in position

and unable to slide past eachother

meaning of memory polymer

(can be deformed but) return to their original shape (when heated or cooled)

Name the monomers from which starch and proteins are produced.

starch - glucose

proteins - amino acids

combustion of hydrocarbons is endothermic / exothermic

EXOTHERMIC

Nonane will condense lower in a fractionating column during fractional distillation than the other alkanes in Table 1.

Explain why.

You should refer to the temperature gradient in the fractionating column.

(nonane) has a higher boiling point

(so nonane) condenses where the column has a higher temperature

Compare ethane with ethene. You should refer to their structure

Structure and bonding

both are hydrocarbons

both contain two carbon atoms (per molecule)

ethane contains six hydrogen atoms (per molecule) (but) ethene contains four hydrogen atoms (per molecule)

both have covalent bonds

ethane contains a single C—C bond (but) ethene contains a double bond

both contain C—H bonds • both small molecules

Compare ethane with ethene. You should refer to reacting

1. both react with oxygen in complete combustion reactions

2. to produce water and carbon dioxide

3. both react with oxygen in incomplete combustion reactions to produce water, carbon monoxide and carbon

4. incomplete combustion is more likely with ethene

5. ethene decolourises bromine water (but) ethane does not decolourise bromine water

6. ethene is more reactive (than ethane)

7. ethene can react with hydrogen (to produce ethane)

8. ethene can react with water (to produce ethanol)

9. ethene can react with halogens (to produce halogenoalkanes)

10. ethene can undergo addition reactions

11. ethene can polymerise (to produce poly(ethene))

what type of reaction produces ethanoic acid from ethanol

oxidation reaction

Why do ethanoic acid and hydrochloric acid have different pH?

Ethanoic acid is a weak acid, HCL is a strong acid. This is because Ethanoic acid doesn't fully dissociate in solution where as HCL does.

higher ph means

more alkaline

volatile meaning

Volatile substances have a tendency to vaporize whereas non volatile substances do not have a tendency to vaporize

thermosoftening plastics

Thermosoftening plastics do not have covalent bonds between neighbouring polymer molecules, so the molecules can move over each other when heated and the plastic melts.

what type of material is glass fibers

fiber-reinforced plastic

what type of material is polyester

matrix

The outer skin makes the surfboard more expensive. Suggest two reasons why an outer skin is added to the poly(styrene) core.

any two from: (to make the board)

• harder

• stronger

• tougher

• more rigid

• waterproof

what two pieces of measuring apparatus could the student use to find the rate of production of hydrogen gas

gas syringe

stop clock

how does magnesium being fixed to steel ships prevent the ship from rusting

magnesium is more reactive, it provides a sacrificial reaction

explain why aluminium window frames do not corrode after they are made

coating of Aluminium oxide protects metal from further corosion

describe a test to show that the drinking water contained aluminium ions (3 MARKS)

1. dissolved in excess sodium hydroxide

2. dissolves in excess to form a colourless solution

3. white precipitate forms which dissolves in excess

describe a test to show that drinking water contains sulfate ions

1. barium chloride

2. hydrochloric acid

3. white precipitate

formula of ethanol

C2H5OH

Methanol is used to produce methanoic acid. What type of substance reacts with methanol to produce methanoic acid?

oxidising (agent)

The mixture of gases from the reactor cools in the condenser. Suggest why ammonia condenses but the other gases do not. (harber process)

ammonia has a higher boiling point

plan an investigation to find the total mass of dissolved solids in an 100cm^3 sample of drinking water

• weigh (evaporating) basin / dish

• add measured volume of water

• weigh (evaporating) basin / dish and water

• heat to evaporate water

• reweigh

• repeat heating until constant mass obtained

• subtract mass of (evaporating) basin / dish from mass

• repeat and calculate a mean, discarding anomalous results

• calculate the mass in 100 cm3 water if necessary

explain how methane keeps titan warmer than other moons of saturn

(methane) allows short(er) wavelength radiation to pass through (from the sun)

(which is) re-emitted from the surface as long(er) wavelength radiation

(which is) absorbed (by methane in the atmosphere)

explain why HDPE has a higher density than LDPE

(in HDPE) polymer chains / molecules are closer together

(so) more atoms per unit volume

give a test to identify the group 1 metal ion in potash alum

flame test

lilac (flame)

name one instrumental method that could identify the group 1 metal ion and show the concentration of the ion in a solution of ptash alum

flame emission spectroscopy

describe how copper is extracted from low grade iron ores by Phyto mining

grow plants (on land containing copper ores)

plants are burnt (to produce ash)

ash dissolved in acid (to produce a solution of a copper compound)

electrolysis of solution (containing a copper compound) or displacement (of copper) from solution (containing a copper compound)

if the FOWARD reaction is exothermic, higher temperature is ________ yield

higher temperature gives lower yield because the reaction is exothermic

Give one other way of changing the rate of reaction between gases. You should not refer to pressure in your answer.

change the temperature

add a catalyst

if the tube is dipped into the solution, what problem would be caused

(sulfuric) acid will travel up tube or

no hydrogen / gas will be collected

explain why a low pressure was used for this reaction

higher yield (of hydrogen or carbon monoxide or product)

(because) fewer moles / molecules / particles on left hand side

What is meant by equilibrium?

IN A CLOSED SYSTEM

the forwards and backwards reactions are equal

The Earth's early atmosphere

1. One theory suggests that during the first billion years of the Earth’s existence, there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans.

2. At the start of this period, the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas. Volcanoes also produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia.

3. When the oceans formed carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, and reducing the amount of carbon dioxide in the atmosphere.

why is evidence for the earths early atmosphere limited

Evidence for the early atmosphere is limited because of the time scale of 4.6 billion years.

explain why increasing the use of biofuels may cause food shortages

fertile land is used for biofuels

less space for actual food

The percentages of nitrogen and of oxygen in the Earth’s atmosphere today have changed from the percentages in the Earth’s early atmosphere.

how much has nitrogen & oxygen increased

nitrogen Increased by about 40 times

oxygen increased by about 21%

Solar energy may not be able to replace the generation of electricity from fossil fuels completely. Suggest two reasons why.

• sunshine is unreliable

• increased demand for energy '

• lack of space

ignore references to cost

what does an exothermic reaction profile look like

reactants up

products down

what does an endothermic reaction profile look like

reactants down

products up

test for carbon dioxide

turns limewater milky

affinity

tendency of a chemical species to react with another to form a chemical compound

desalination

the process of removing salt from seawater.

effluent

liquid waste or sewage discharged into a river or the sea.

leachate

1. water that has percolated through a solid and leached out some of the constituents.

bronze is an alloy of and , used for making _________ and

copper

tin

statues

decorative things

brass is an alloy of and , used for making _________ and

copper

zinc

taps

door fittings

gold is used for made of , and

jewellery

silver

copper

zinc

pure gold is __ carrats

24

18 carrat gold is ___% gold

75%

high carbon steel is ______ but

____________

stong

brittle

low carbon steel is ________ and

_____________ shaped

softer

more easily

steels containing _________ and _________ are stainless steels.

and is and____ to corrosion

chromium and nickel

hard and resistant

what is borosilicate glass made from

sand, boron, trioxide

borosilicate glass melts at ____________ temps than soda lime glass

higher

Most composites are made of two materials:

a matrix or binder surrounding

binding together fibres or fragments of the other material is called what

reinforcement

sewage treatments

what is bioleaching

when you use bacteria to produce leachate solutions that contain metal compounds

aluminium magnesium alloys are _____ density and used in ____________ manafacturing

low

aerospace

test for carbonate ions

• add hydrochloric acid

• effervescence / fizzing

• bubble gas through limewater

• limewater becomes cloudy

does the iron nail rust?

Tube 3: (nail) does not rust because no air / oxygen

Magnesium is fixed to some steel ships.

Explain how this prevents the steel from rusting.

magnesium is more reactive (than iron) (so magnesium) provides sacrificial protection

Plan an investigation to find the total mass of dissolved solids in a 100 cm3 sample of the drinking water.

• weigh (evaporating) basin / dish

• add measured volume of water

• weigh (evaporating) basin / dish and water

• heat to evaporate water

• reweigh

• repeat heating until constant mass obtained

• subtract mass of (evaporating) basin / dish from mass

• repeat and calculate a mean, discarding anomalous results

• calculate the mass in 100 cm3 water if necessary

Explain why these organisms could not have evolved in the same way that life is thought to have evolved on Earth.

(Titan has) little / no oxygen

(so) photosynthesis has not occurred (on Titan)

little carbon dioxide present OR oxygen-using animals cannot have evolved

Titan is warmer than the other moons of Saturn because its atmosphere contains the greenhouse gas methane. Explain how this greenhouse gas keeps Titan warmer than the other moons of Saturn

(methane) allows short(er) wavelength radiation to pass through (from the sun)

(which is) re-emitted from the surface as long(er) wavelength radiation

(which is) absorbed (by methane in the atmosphere)

Determine the mean rate of reaction in cm3 /s between 2 and 4 minutes for coarse manganese dioxide lumps.

0.092

what is phytomining

plants are grown in soil that contains low grade ore.

the plants absorb metal ions through their roots and concentrate these ions in their cells.

the plants are harvested and burnt.

the ash left behind contains metal compounds.

how does iron rust

iron + oxygen + water → hydrated iron(III) oxide

Hydrated iron(III) oxide is the orange-brown substance seen on the surface of rusty objects.

ways to prevent corrosion

• painting

• oiling and greasing

• coating with plastic

• Electroplating

• Sacrificial protection

Electroplating

Electroplating involves using electrolysis to put a thin layer of a metal on the object:

sacrificial protection

Iron can be protected from rusting if it is in contact with a more reactive metal, such as zinc.

The more reactive metal oxidises more readily than iron, so it ‘sacrifices’ itself while the iron does not rust.

Once the sacrificial metal has corroded away, it can simply be replaced.

Galvanising

When iron is coated in zinc, the process is called galvanisation. The zinc layer stops oxygen and water reaching the iron. Zinc is more reactive than iron, so it also acts as a sacrificial metal.