Topic 5 - Transition Metals/alloys, Dynamic Equilibria, Quantitative Analysis & Chemical/fuel Cells Flashcards

Question 1

Q

Many metals corrode.
An experiment is carried out to see if magnesium ribbon wrapped around a piece of iron rod has an effect on the rate at which the iron rod rusts. Method:
• an iron rod, with magnesium ribbon wrapped around it, is placed in boiling tube A
• 10 cm3 water from a measuring cylinder is poured into this boiling tube
• an identical rod but with no magnesium ribbon wrapped around it is placed in a 2nd
boiling tube - B
• 10 cm3 water from a measuring cylinder is poured into this boiling tube.
Both boiling tubes are left for a few days.
Explain why iron rod rather than stainless steel rod is used in this experiment. (2)

State why it is not necessary to use a pipette to measure out 10 cm3 water. (1)

Answer

A

Stainless steel is resistant to corrosion/rusting/corrosion rate is lower (1)
Neither rod would rust/react in a few days (1)

Measuring cylinder is accurate enough/accuracy of pipette is not needed (1)

Question 2

Q

• an iron rod, with magnesium ribbon wrapped around it, is placed in a boiling tube
labelled A
• 10 cm3 water from a measuring cylinder is poured into this boiling tube
• an identical rod but with no magnesium ribbon wrapped around it is placed in a second
boiling tube labelled B
• 10 cm3 water from a measuring cylinder is poured into this boiling tube.
After a few days the two boiling tubes were examined.
Explain the results of this experiment. (2)
Boiling tube A = appearance of iron rod hasn’t changed, magnesium has started to disappear
Boiling tube B = a small amount of brown deposit has formed around the rod

Answer

A

A has corroded/rusting has taken place in B (1)
Because magnesium is more reactive than iron (1)

Question 3

Q

Painting iron objects prevents corrosion.
Explain why painting iron objects prevents corrosion. (2)

Answer

A

The paint acts as a protective barrier (1)
Excludes air/water/oxygen (1)

Question 4

Q

Corrosion of iron objects can be prevented by painting them or by electroplating them.
State one other way of preventing the corrosion of iron objects. (1)

Answer

A

Sacrificial protection

Question 5

Q

Copper is a transition metal.
Magnesium reacts with copper sulfate solution to form copper and a solution of magnesium
sulfate.
Magnesium sulfate solution is colourless.
Describe two changes you would see during this reaction. (2)

Answer

A

Colour/blue fades/colourless solution forms (1)
Red-brown solid forms (1)
Magnesium disappears (1)

Question 6

Q

Pure metals are often converted into more useful alloys.
E.g., aluminium is converted into an alloy used in aircraft, iron is converted into an alloy used in cutlery and gold alloys are used in jewellery.
These processes of alloying change the structures of the metals.
Explain how alloying changes these pure metals to make the alloys more suitable for the given uses. (6)

Aluminium- 2.7g/cm^3 easy to bend, weak
Iron- 7.75g/cm^3 easy to bend, weak
Gold- 19.3g/cm^3 easy to bend, weak

Answer

A

• an alloy is a mixture of metals
• because larger/different sized atoms introduced in alloying,
• stop layers moving easily over one another
• therefore individual alloy is stronger/harder
• an aluminium alloy is magnalium
• pure aluminium is not suitable for making aircraft as it bends too easily / too weak
• aluminium alloy stronger
• magnesium atoms lighter than aluminium atoms,
• therefore alloy still low density / lower density than aluminum alone
• an iron alloy is stainless steel
• pure iron is not suitable for cutlery as it bends too easily / too weak
• iron corrodes,
• corrosion would contaminate food
• stainless steel does riot corrode
• gold alloy harder
• therefore more hard wearing
• gold alloys less likely to change shape when worn
• alloying can change the colour of the gold

Question 7

Q

Pure metals can be made more useful by converting them into alloys or by electroplating them.
Explain what alloying and electroplating are and how they can make metals more useful. (6)

Answer

A

• in an alloy another metal is added / a mixture of metals
• in a pure metal, all atoms are of the same size • layers of atoms can slide over one another easily
• so a pure metal is malleable / soft
• alloys are stronger
• because atoms of different sizes
• disrupt layers of atoms in the alloy
• layers cannot slide
• alloys can be used e.g. in metal beams / airplanes parts / bridges
• because the alloy is stronger than the pure metal
• electroplating means that a (corrosion resistant) metal {coating / layer} is added on top of the (pure) metal / alloy • (more reactive) metals can corrode when exposed to air and water • (corrosion resistant) metal coating does not react with oxygen in air • therefore pure metal object does not corrode • object remains shiny • object looks more attractive • base metal is often cheaper e.g. copper plated with gold in jewellery • therefore object may be cheaper • electroplating involves creating a circuit • object to be plated is made the cathode • plating metal is the anode • electrolyte made from plating metal salt solution

Question 8

Q

Alloys of gold are often used to make jewellery.
The purity of gold is measured in carats.
Different alloys of gold have different carats.
18 carat gold. 75% gold, 15% silver, 10% copper
24 carat gold. 100% gold, 0% silver and copper
Explain why 18 carat gold is stronger than 24 carat gold. (2)

Answer

A

18 carat gold contains atoms of different sizes (1)
Prevents layers from sliding over one another (1)

Question 9

Q

Aluminium alloys are used instead of pure aluminium in aircraft manufacture.
Explain, in terms of the arrangement of metal particles, why aluminium alloys are stronger
than pure aluminium. (3)

Answer

A

In pure aluminium, all of the atoms are the same size, whereas in aluminium alloys, the atoms are all different sizes (1)
In aluminium, layers of atoms easily slide over each other (1)
In alloy, layers cannot easily slide over each other (1)

Question 10

Q

Explain why covering iron tools with a thin layer of grease prevents rusting. (2)

Answer

A

Air/oxygen excluded (1)
Water excluded (1)
Air/oxygen/water need for corrosion (1)

Question 11

Q

Sacrificial protection is another way of preventing rusting.
An example of sacrificial protection is when lumps of zinc are connected to the iron-containing structure of an oil rig.
Explain how the zinc protects the iron from rusting. (2)

Answer

A

Zinc is more reactive than iron (1)
So reacts instead (1)

Question 12

Q

Alloys are mixtures of two or more metals.
Magnalium is an alloy of magnesium and aluminium. It is often used for aircraft parts.
Aluminium-2.7g/cm^3 low strength high resistance to corrosion
Magnalium- 2g/cm^3 high strength very high resistance to corrosion
Explain, using the information, why magnalium, rather than pure aluminium, is used for aircraft parts. (3)

Answer

A

Magnalium has a lower density than aluminium (1)
Magnalium is stronger than aluminium (1)
Magnalium has a higher resistance to corrosion than aluminium (1)

Question 13

Q

Iron rusts when it is left in certain conditions.
The apparatus used to investigate the rusting of some iron nails:
A- test tube with air + water
B- test tube with air + drying agent
C- test tube with oil + boiled water
Explain why the iron nail in tube A would rust but the iron nails in tubes B and C would
not rust. (3)

Answer

A

Both water and oxygen is needed for rusting (1)
Tube a has both water and oxygen present (1)
Tube b has no water present (1)
Tube c has only water present (1)

Question 14

Q

Magnesium is more reactive than iron.
An iron nail is wrapped with a strip of magnesium around it, placed in some water.
The tube was left for a few days.
State what would happen to this iron nail. (1)

Answer

A

No rusting/doesn’t corrode

Question 15

Q

When iron rusts, a brown solid forms on the surface of the iron.
What happens to the iron as the rust forms?
(1)
A the iron is hydrated
B the iron is neutralised
C the iron is oxidised
D the iron is reduced

Answer

A

the iron is oxidised

Question 16

Q

An iron bucket is coated in zinc.
Over many years of use, the iron bucket has been scratched and left outside in the rain.
Although some of the zinc coating has been removed to expose iron, the iron bucket has not rusted.
Explain why the iron has not rusted. (2)

Answer

A

Iron hasn’t rusted because zinc is more reactive than iron (1)
So zinc corrodes instead of iron (1)

Question 17

Q

Alloy steels are made when iron is alloyed with other transition metals such as cobalt and
chromium.
Iron fences can be galvanised by coating them with a layer of zinc. When the layer of zinc is
scratched exposing the iron to the weather, the iron does not rust.
Explain why the exposed iron does not rust. (2)

Answer

A

Zinc corrodes in preference to iron/zinc reacts with air and water instead (1)
Zinc is more reactive than iron/is a sacrificial (1)

Question 18

Q

Alloys are mixtures of 2 or more metals.
Brass is an alloy of copper.
Brass pins are used in an electric plug.
Brass is harder than copper.
Give a reason why using a harder substance for the pins is an advantage. (1)

Answer

A

Pins do not bend

Question 19

Q

Give 2 advantages for electroplating some metal objects (2)

Answer

A

Improve appearance (1)
Help prevent corrosion (1)

Question 20

Q

Give one reason why metals are electroplated. (1)

Answer

A

Improve appearance/more corrosion resistant

Question 21

Q

The rate of rusting can be increased by using sea water.
Describe a simple experiment to compare how much an iron nail rusts in sea water when
compared to water. (3)

Answer

A

Clean iron nails (1)
Place nails into separate test tubes of water and seawater (1)
Leave test tubes for a period of time (1)
Observe the test tubes and record any changes to compare appearance/mass

Question 22

Q

Alloys are mixtures of two or more metals.
Alloy steels are formed when other metals are mixed with iron.
Cutlery is made of stainless steel.
Give two reasons why cutlery is made of stainless steel rather than iron. (2)

Answer

A

Stainless steel doesn’t rust/cortode (1)
Stainless steel is tronger (1)

Question 23

Q

Metal objects can be electroplated with gold.
Give two reasons why metal objects are electroplated with gold. (2)

Answer

A

Improve the appearance (1)
Increase resistance to corrosion (1)

Question 24

Q

The pure metals aluminium, copper and gold and the alloys brass and magnalium are used
to make many useful articles.
The way in which these metals and alloys are used is related to their properties, such as their density, electrical conductivity, resistance to corrosion and strength.
State some uses of aluminium, copper, gold, brass and magnalium and explain how each use is related to their properties. (6)

Answer

A

• suitable use of aluminium eg cooking foil
• related property - malleable, low toxicity, low reactivity
• suitable use of copper eg water pipes
• related property - low reactivity
• suitable use of gold eg electronic contacts
• related property - does not corrode, good electrical conductor
• suitable use of brass eg pins for electric plugs • related property - strong and hard wearing
• suitable use of magnalium eg aircraft parts
• related property - low density

Question 25

Q

Gold alloys can be used to repair teeth.
One reason that gold alloys are used is that they can be hammered into shape.
Give one other reason why gold alloys are used to repair teeth. (1)

Answer

A

Doesn’t corrode/insoluble/inert

Question 26

Q

In a hydrogen-oxygen fuel cell, hydrogen and oxygen react at the electrodes.
Some metal objects are electroplated.
State two reasons for electroplating a metal object. (2)

Answer

A

Improves the appearance/shiny (1)
Improves resistance to corrosion (1)
Can make an object look more expensive than it actually is (1)

Question 27

Q

Transition metals have many uses.
Most iron produced is converted into alloys of iron.
State why alloys have more uses than pure metals. (1)

Answer

A

Alloys are stronger/more corrosion resistant

Question 28

Q

Platinum acts as a catalyst.
State, in terms of its position in the periodic table, why you would expect platinum to act as a catalyst. (1)

Answer

A

Platinum is a transition element

Question 29

Q

Many metals corrode.
Hydrazine, N2H4, reacts with oxygen.
N2H4 + O2 → N2 + 2H2O
A metal in water corrodes faster than an identical piece of metal in the same volume of water containing dissolved hydrazine.
Use the information to explain how hydrazine slows corrosion. (2)

Answer

A

Oxygen is removed by the hydrazine (1)
Oxygen is needed for rusting/corrosion (2)

Question 30

Q

Alloy steels are made when iron is alloyed with other transition metals such as cobalt and
chromium.
Explain how lubricating a bicycle chain with oil prevents corrosion of the steel chain. (2)

Question 31

Q

State the meanings of the terms actual yield and theoretical yield. (2)

Answer

A

Actual yield - Mass of product formed in reaction (1)
Theoretical yield - calculated mass of products formed using the balanced equation/calculated mass of products if all reactants used to form products only with no losses (1)

Question 32

Q

State two reasons why the actual yield of a reaction is usually less than the theoretical yield. (2)

Answer

A

Some reactants remained un reacted (1)
Side reactions may occur (1)
Some product is lost during the reaction (1)

Question 33

Q

The concentration of dilute sulfuric acid can be determined by titration with sodium hydroxide
solution of known concentration.
- 25.00 cm3 of dilute sulfuric acid was measured out using a pipette and transferred to a conical flask.
- A few drops of methyl orange indicator were added to the acid in the conical flask. Sodium
hydroxide solution was added to the acid from a burette until the indicator changed colour.
- The titration was repeated until 2 concordant results were obtained.
- The accurate result was the average of the two concordant results.
Further detail can be added to this method to ensure that anyone following the method will
obtain an accurate result.
Explain 2 details that could be added to this practical method to ensure an accurate result
is obtained. (4)

Answer

A

read bottom of the meniscus on the burette/pipette scale / read burette/pipette at eye-level (1) to obtain accurate volume of sodium hydroxide solution / sulfuric acid added (1)
add alkali 1 drop at a time near end point (1) to identify exactly when colour change of indicator takes place (1)
use a white tile (1) to make it easier to see exactly when colour change of indicator takes place (1)
make sure no air bubbles in burette or pipette when measuring volumes (1) so exact volumes are recorded (1)
continually swirl flask (1) to ensure complete mixing of acid with alkali (1)
wash inside of conical flask with a little deionised/distilled water (1) to wash reactants into reaction mixture (1)
wash burette / pipette with appropriate solution before titration (1) to ensure burette / pipette is riot contaminated (1)

Question 34

Q

A titration is to be carried out to find the concentration of a solution of sodium hydroxide.
The sodium hydroxide solution is titrated with dilute sulfuric acid.
The available apparatus includes a burette, a pipette, a funnel, a conical flask & an indicator.
State 1 safety precaution that must be taken when using sodium hydroxide solution and dilute sulfuric acid. (1)

Answer

A

Wear gloves to prevent contact with skin/safety (1)
Spectacles to prevent contact with eyes (1)

Question 35

Q

Write the balanced equation for the reaction of dilute sulfuric acid, H2SO4, with sodium
hydroxide. (2)

Answer

A

2NaOH + H2SO4 → Na2SO4 + 2H2O

Question 36

Q

The method used to make the lead sulfate is:
• pour 100 cm3 lead nitrate solution into a beaker
• add drops of sodium sulfate solution until a precipitate is seen
• allow the precipitate to settle to the bottom of the beaker
• pour off the liquid
• use a spatula to transfer the solid lead sulfate onto a filter paper.
Explain two ways of improving this experiment in order to increase the amount and quality of lead sulfate that could be obtained from 100 cm3 of lead nitrate solution. (4)

Answer

A

Add excess sodium sulfate solution rather than a few drops (1) so more reaction occurs to form more lead sulfate (1)
Filter the reaction mixture rather than pour off the liquid (1) so none of the lead sulfate is lost in separation (1)
Wash the lead sulfate (1) so the impurities are removed (1)
Place the lead sulfate in an oven/warm place (1) so the lead sulfate is dry (1)

Question 37

Q

The mass of solid left in the crucible is less than the theoretical mass of calcium oxide that should be obtained. A possible reason for this is that (1)
A some solid was lost from the crucible
B the solid remaining absorbed some water from the air
C some carbon dioxide remained in the crucible
D the decomposition was incomplete

Answer

A

some solid was lost from the crucible

Question 38

Q

A student wanted to find the volume of dilute hydrochloric acid that would react with 25.0
cm3 of lithium hydroxide solution.
They used some equipment to carry out a rough titration and then a further 2 accurate titrations.
Describe how the rough titration should be carried out once the dilute hydrochloric acid,
lithium hydroxide solution and indicator are placed in the burette and conical flask. (4)

Answer

A

Read the initial volume of the burette (1)
Open the tap/add acid to alkali (1)
Swirl the mixture (1)
Until endpoint/indicator changes colour (1)
Close the tap, then read the final volume of acid in burette (1)

Question 39

Q

Describe the experimental procedure to carry out a titration to find the exact volume of
sulfuric acid needed to neutralise 25.0 cm3 of sodium hydroxide solution and obtain pure, dry
crystals of sodium sulfate. (6)

Question 40

Q

The volume of dilute sulfuric acid required to neutralise 25.0 cm3 of ammonia solution can be found by titration.
In the titration, a few drops of methyl orange indicator were added to the ammonia solution in a conical flask before adding the dilute sulfuric acid.
The titration was repeated to obtain a mean volume of dilute sulfuric acid required to
neutralise the 25.0 cm3 of ammonia solution.
The volumes of the 2 solutions were measured accurately.
Explain 2 other practical steps that should be used in the titration to ensure that an accurate titre volume is obtained. (4)

Answer

A

use of white tile (1) easier to see precisely when indicator changes colour (1)
near to end point add acid slowly/in small quantities each time (1) easier to stop excess acid being added (when indicator changes colour) (1)
swirl flask when adding acid (1) ensures complete mixing of both reactants (1)
touch tip of burette on inside wall of flask and/or rinse walls of flask (1) ensures all acid takes part in reaction (1)
rinse burette with acid/pipette with ammonia/flask with water beforehand (1) no impurities to affect result (1)
remove funnel from burette (1) to stop any extra drop of acid falling into burette (1)

Question 41

Q

Methane reacts with steam to form hydrogen and carbon dioxide.
The reaction takes place in 2 stages.
Stage 1: CH4(g) ↔️ 3H2(g) + CO(g)
Stage 2: CO(g) + H2O(g) ↔️ H2(g) + CO2(g)
Stage 1 takes in heat energy, it is endothermic.
Explain the effect of increasing the temperature on the yield of the products of stage 1.

Answer

A

Shift equilibrium to the right/forward direction (1)
Increase yield of product (1)

Question 42

Q

Potassium hydroxide reacts with hydrochloric acid to form potassium chloride and water.
potassium hydroxide + hydrochloric acid → potassium chloride + water
A student carried out a titration to find the exact volume of dilute hydrochloric acid that
reacted with 25.0 cm3 of potassium hydroxide solution.
There were 5 steps in the titration.
The steps shown are not in the correct order.
step J - pour the potassium hydroxide solution into a conical flask and add a few drops of indicator to this solution
step K - fill a burette with the dilute hydrochloric acid and record the initial reading from the burette
step L - use a measuring cylinder to obtain 25 cm3 of potassium hydroxide solution
step M - take a final reading from the burette & calculate the volume of the dilute hydrochloric acid reacted
step N - run the dilute hydrochloric acid from the burette into the conical flask until the indicator changes colour.
A student was then asked to produce a pure sample of solid potassium chloride.
After finding the volume of acid reacted in step M, the student added this volume of acid to a
fresh 25.0 cm3 sample of the potassium hydroxide solution.
This mixture was then evaporated.
Explain why this new mixture was evaporated rather than the original mixture from the titration, to produce a pure sample of solid potassium chloride. (2)

Answer

A

Solution from titration contains an indicator (1)
Indicator would contaminate salt (1)

Question 43

Q

There were 5 steps in the titration.
The steps shown are not in the correct order.
step J - pour the potassium hydroxide solution into a conical flask and add a few drops of indicator to this solution
step K - fill a burette with the dilute hydrochloric acid and record the initial reading from the burette
step L - use a measuring cylinder to obtain 25 cm3 of potassium hydroxide solution
step M - take a final reading from the burette & calculate the volume of the dilute hydrochloric acid reacted
step N - run the dilute hydrochloric acid from the burette into the conical flask until the indicator changes colour.
Write the steps in the correct order (1)

Answer

A

K L J N M

Question 44

Q

A titration of sodium hydroxide solution with hydrochloric acid can be carried out as follows:
1 - a pipette is used to measure 25.00 cm3 of sodium hydroxide solution into a conical flask
2 - a few drops of indicator are added to the sodium hydroxide solution
3 - the burette is filled with hydrochloric acid
4 - the hydrochloric acid is added to the sodium hydroxide solution until the indicator changes colour.
Describe how the pipette should be used to measure exactly 25.00 cm3 of sodium hydroxide solution into the conical flask. (2)

Answer

A

Use a pipette filter (1)
Wash pipette with sodium hydroxide solution (1)
Draw the liquid up so the bottom of the meniscus touches the line (1)

Question 45

Q

The burette is first washed with water.
It is then rinsed with some of the acid before it is filled with the acid to begin the titration.
Explain why the burette is rinsed with the acid. (2)

Answer

A

To remove water from the burette (1)
Because this would dilute the original acid (1)
This will give an inaccurate result (1)

Question 46

Q

The industrial production of sulfuric acid involves several steps.
One of these steps is the reaction of sulfur dioxide, SO2, with oxygen to form sulfur trioxide, SO3.
What volume of sulfur trioxide, in dm3, is produced by the complete reaction of 750 dm3 of sulfur dioxide?
(all volumes of gases are measured under the same conditions of temperature and
pressure) (1)
A 375.5
B 750
C 1125.5
D 1500

Question 47

Q

The volume of dilute sulfuric acid required to neutralise 25.0 cm3 of ammonia solution can be
found by titration.
In the titration, a few drops of methyl orange indicator were added to the ammonia solution in
a conical flask before adding the dilute sulfuric acid.
When the ammonia solution was neutralised by the dilute sulfuric acid, a solution of
ammonium sulfate was formed.
Complete the balanced equation for the reaction between ammonia solution and sulfuric acid. (2)
………… NH3 + H2SO4 → ……………..

Answer

A

2NH3 + H2SO4 → (NH4)2SO2

Question 48

Q

Ammonia solution and dilute sulfuric acid are used to prepare pure, dry ammonium sulfate
crystals.
In an experiment a titration is carried out to determine the volumes of ammonia solution and dilute sulfuric acid that react together.
Then an ammonium sulfate solution is prepared from which the pure, dry crystals are
obtained.
Describe in detail, using suitable apparatus, how this experiment should be carried out. (6)

Answer

A

• pipette to measure out the ammonia solution (25 cm3)
• into a suitable container, e.g. conical flask
• add few drops of methyl orange indicator
• put flask on a white tile
• fill burette with sulfuric acid solution
• read level of liquid in burette
• add acid from the burette
• swirl flask gently / mix
• add drop-wise near end-point
• until {indicator just changes colour}
• read level on burette
• repeat experiment until concordant results
• mix the same volumes of sulfuric acid and ammonia solution (determined from the titration experiment)
• but leaving out the indicator/methyl orange
• pour solution into an evaporating dish
• heat the solution to point of crystallisation
• leave to cool
• filter off crystals
• leave to dry

Question 49

Q

Ammonium sulfate and ammonium nitrate are used as fertilisers as they both contain
nitrogen, which will increase the yield of crops.
Suggest one other reason for using solid ammonium sulfate and solid ammonium nitrate as nitrogenous fertilisers. (1)

Answer

A

Both are soluble/dissolve in water (1)

Question 50

Q

Ammonium nitrate can be made by the reaction of ammonia with nitric acid.
Write the balanced equation for this reaction. (2)

Answer

A

NH3 + HNO3 → NH4NO3

Question 51

Q

Describe one similarity and one difference between the industrial production of
ammonium sulfate and the laboratory
preparation of ammonium sulfate. (2)

Answer

A

Both use sulfuric acid (1)
Both are examples of neutralisation (1)
Industrial process is on a much larger scale than the laboratory process (1)
The industrial process involves much more stages than the laboratory process (1)
Ammonia is a gas in the industrial process but a solution in the laboratory process (1)
Laboratory preparation uses titration and crystallisation (1)

Question 52

Q

When hydrogen is removed from an alkane, an alkene is formed.
This is an example of a dehydrogenation reaction.
Under certain conditions the dehydrogenation of propane forms propene and a dynamic
equilibrium is reached.
State what is meant by dynamic in this context. (1)

Answer

A

Both forward and backwards reactions take place at the same time (1)

Question 53

Q

C3H8(g) ↔️ C3H6(g) + H2(g)
The forward reaction takes in heat energy and is endothermic. A manufacturer produces large quantities of propene using this equilibrium reaction.
Suggest, with explanations, suitable conditions that the manufacturer could use to maximise the yield and rate of production of propene from propane. (6)

Answer

A

use of suitable catalyst (any suitable metal eg Pt)
helps increase rate of forward reaction and
helps increase rate of back reaction
so increases rate of attainment of equilibrium - but has no effect on equilibrium yield
increase temperature would increase rate of reaction
shifts equilibrium to right hand side
so increases equilibrium yield
so use a high temperature (range 200-600 °C - anything would be reasonable)
use of very high temperatures increases energy use
so makes product more expensive
as fewer molecules on left hand side than right
so use low pressures
moves equilibrium to right hand side
so increases equilibrium yield
high pressure increases rate but decreases yield OR low pressure increases yield but decreases rate
pressure used is a compromise between rate and yield

Question 54

Q

The reaction between nitrogen and hydrogen is exothermic.
If nitrogen and hydrogen were reacted at 150 atm pressure and 300 °C, without a catalyst, some ammonia would be formed.
In the Haber process a pressure of 150 atm and a temperature of 450 °C are used, in the
presence of an iron catalyst.
Explain why the conditions used in the Haber process are better than the first set of conditions for the manufacture of ammonia. (6)

Answer

A

The effect of the temperature rise on the rate of attainment of equilibrium and on the equilibrium yield are considered by:
• higher temperature reaches equilibrium faster because molecules move faster
• therefore there are more frequent collisions because molecules have more energy
• therefore more collisions have required energy but yield will be lower
• because higher temperature favours endothermic reaction and so equilibrium shifts to left hand side
• which is decomposition of ammonia / ammonia reforms elements
• catalyst causes reaction to reach equilibrium faster / catalyst increases rates (of both forward and back reactions)
• lowers the activation energy (of both forward and back reactions) but does not affect yield
• equilibrium position not affected.

Question 55

Q

In industry, ammonia is manufactured by reacting nitrogen with hydrogen.
Write the word equation for this reaction, including the correct symbol to show that the
reaction is reversible. (3)

Answer

A

Nitrogen + hydrogen ↔️ ammonia

Question 56

Q

Explain the importance of fertilisers in farming (2)

Answer

A

Crops require fertilisers to grow (1)
Fertilisers contain N, P and K compounds (1)
Promote plant growth (1)
Increased yield (1)

Question 57

Q

Fertilisers contain compounds that promote plant growth.
State the name of an element in these compounds that promotes plant growth. (1)

Question 58

Q

Potassium nitrate is present in some fertilisers.
Potassium nitrate is formed by the reaction of potassium hydroxide solution with nitric
acid.
Complete the balanced equation for this reaction. (2)
KOH + HNO3 → ……………. + ………………..

Answer

A

KOH + HNO3 → KNO3 + H2O

Question 59

Q

Fertilisers are sometimes added to soil.
State why fertilisers are added to soil. (1)

Answer

A

To make plants grow faster/bigger/more

Question 60

Q

Hydrogen and oxygen are reactants in some fuel cells.
Which word equation shows the overall reaction that occurs in these fuel cells? (1)
A hydrogen + oxygen → hydroxide
B hydrogen + oxygen → sulfuric acid
C hydrogen + oxygen → water
D hydrogen + oxygen → hydrochloric acid

Answer

A

hydrogen + oxygen → water

Question 61

Q

Complete the half-equation for the reaction taking place at one of the electrodes in a
hydrogen-oxygen fuel cell. (2)
O2 + ………….. H+ + ………….. → ………… H2O

Answer

A

O2 + 4H+ + 4e- → 2H2O

Question 62

Q

Chemical cells produce a voltage.
A chemical cell can be made by placing the metals copper and zinc in a beaker of sodium
chloride solution.
Describe what will happen to the brightness of the light bulb over a long period of time. (2)

Answer

A

Starts bright (1)
Becomes dimmer (1)
Goes out (1)

Question 63

Q

A torch contains a chemical cell.
The torch is turned on and then left on for many hours.
Describe what you would see happen when the torch is turned on and then left for many hours. (2)

Answer

A

Bright light at start (1)
Fades/gets dimmer (1)
Then goes out (1)

Question 64

Q

Hydrogen-oxygen fuel cells can be used to provide electrical energy in a spacecraft.
The reaction that takes place in the fuel cell is
hydrogen + oxygen → water
Evaluate the advantages and disadvantages of providing electrical energy in a spacecraft
using hydrogen-oxygen fuel cells rather than chemical cells. (6)

Answer

A

advantages:
• once set up, fuel cells require no maintenance • chemical cells will need to be replaced / chemical cells have a limited lifetime
• fuel cells operate as long as reactants are supplied
• voltage drops in chemical cells as reactants are used up
• once used chemical cells cannot be used again or need re-charging
• used chemical cells take up valuable space on spacecraft
• new chemical cells need to be transported to spacecraft
• used chemical cells need to be transported back to earth
• water produced in the fuel cell is the only product
• water can be used on the spacecraft as drinking water
disadvantages:
• hydrogen and oxygen must be supplied
• gas tanks need to transported by spacecraft
• storage of hydrogen is difficult because it is a gas
• hydrogen is flammable
• fuel cells are expensive to manufacture
conclusion:
• either cell can be chosen as the preferable one but suitable reasons must be given

Answer 61

A

Reactants are being used up

Answer 62

A

Voltage is constant (1)
Chemical cells contain harmful/toxic substances (1)

Answer 63

A

2H2 + O2 → 2H2O

Answer 64

A

Forward and backwards reactions take place at the same time/rate of forward and backward reaction is the same (1)
No overall Chang in the amount of substance/no observable change (1)

Answer 65

A

Higher pressure favours forward reaction/equilibrium shifts to the right (1)
Because decrease in the number of molecules (1)
Yield increases (1)

Answer 66

A

Lower temperature favours forward reaction/equilibrium shifts to the right (1)
Because forward reaction is exothermic (1)
Yield increases (1)

Answer 67

A

Natural gas

Answer 68

A

Forward and backwards reactions takes place/dynamic (1)
At the same time/equilibrium (1)

Answer 69

A

All 3 gases present/nitrogen, hydrogen and ammonia (1)
Ammonia decomposes/turns back to reactants (1)

Answer 70

A

Higher yield (1)
Because fewer gas molecules/moles on RHS/equilibrium shifts to the RHS (1)

Answer 71

A

Rate increased/time to reach equilibrium reduced (1)
Because gas molecules closer/more concentrated (1)
So increased collision rate/more frequent collisions (1)

Answer 72

A

Pipette (1)
Draw liquid up to line/use pipette filler/rinse first/read at eye level (1)

Answer 73

A

soft:
• add soap (solution)
• shake/ mix • lather (immediately)
• no scum/ no precipitate
permanent hard:
• add soap (solution)
• shake
• no lather / less than with soft water
• scum/ precipitate
• boiled sample
• same results / boiling does not change
• becomes soft after ion exchange but not after boiling
temporary hard:
• add soap (solution)
• shake
• no lather / less than with soft water
• scum/ precipitate
• boiled sample
• after boiling precipitate / (lime)scale formed
• lather (immediately)

Answer 74

A

No sharp/clear/distinct change in colour (1)
Gradual colour change (1)
There are too many different colours (1)

Answer 75

A

titration experiment:
• rinse pipette with alkali and burette with acid
• measure alkali using a pipette
• into suitable container e.g. flask/beaker
• add a few drops of indicator / suitable named indicator (eg methyl orange/phenolphthalein)
• flask on a white tile
• fill burette with acid
• read level/volume (of acid) in burette
• add acid from burette to the flask slowly / swirl the flask
• until {indicator just changes colour/correct colour change for named indicator (eg methyl orange yellow to peach/orange, phenolphthalein pink to colourless)/solution is neutral}
• read level/volume (of acid) in burette
• repeat experiment
• until concordant results
salt preparation:
• mix the same volume of alkali with the volume of acid determined from the first experiment but do not add indicator (or add (activated) charcoal to remove indicator, then filter)
• pour solution into an evaporating basin
• {heat solution/leave the water to evaporate} until pure salt crystals are left

Answer 76

A

methyl orange yellow in alkali, orange at end point

Answer 77

A

high melting point

Answer 78

A

potassium and caesium (group 1) copper and iron (transition metals)

Answer 79

A

Regular arrangement of +ve ions/cations (1)
Surrounded by delocalised electrons (1)

Answer 80

A

Electrons (1)
Move/flow (1)

Answer 81

A

Floats (1)
Moves around (1)
Effervescence/fizzing/bubbles (1)
Melts/changes to ball shape (1)
Becomes smaller/disappears (1)

Answer 82

A

2Na + 2H2O → 2NaOH + H2

Answer 83

A

Doesn’t corrode/tarnish (1)
Unreactive (1)
Shiny (1)
Malleable (1)
Expensive/maintains its value (1)

Answer 84

A

Gold atoms all the same size (1)
Layers easily slide over each other (1)
In alloys metal atoms are different sizes (1)
Distrusts structure of gold atoms (1)
Prevents layers of atoms from sliding (1)

Answer 85

A

reactivity series:
• aluminium more reactive than iron/aluminium higher than iron in reactivity series
• aluminium forms stronger bonds with oxygen than iron does
• aluminium oxide more stable (to decomposition) than iron oxide
• aluminium more reactive than carbon/aluminium higher than carbon in reactivity series
cost:
• electrolysis/electricity (more) expensive (than heating with carbon)
• heating with carbon is (relatively) cheap method
Iron:
• carbon more reactive than iron/iron less reactive than carbon
• iron oxide reduced
• by heating with carbon
• no need to use (expensive) electrolysis
Aluminium:
• aluminium oxide difficult to reduce
• aluminium oxide cannot be reduced by (heating with) carbon
• (cheaper) reduction with carbon does not work
• need more powerful method of reduction
• therefore must use electrolysis

Answer 86

A

Hear (1)
With carbon (1)

Answer 87

A

Reduction is the loss of oxygen (1)
Copper (oxide) loses oxygen (1)
Hence copper oxide is reduced (1)
OR
Oxidation is the gain of oxygen (1)
Hydrogen gains oxygen (1)
Hence hydrogen is oxidised (1)

Answer 88

A

When bent/deformed (1)
Shape memory alloys return to their original shape (1)
OR
Shape memory alloys return to their original shape (1)
But other alloys stay deformed (1)

Answer 89

A

Steel corrodes/rusts (1)
Prevents corrosion/rust (1)
Copper doesn’t rust (1)
Copper oxidises slower (1)
Kills bacteria (1)

Answer 90

A

In pure metal, layers slide over each other easily (1)
2nd metal, particles are larger (1)
Disrupt structure (1)
Prevents layers from slipping (1)

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Topic 5 - Transition Metals/alloys, Dynamic Equilibria, Quantitative Analysis & Chemical/fuel Cells Flashcards

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