Halogens

Question 1

Name the product of the reaction between potassium and chlorine.

Potassium chloride

Potassium oxide

Potassium chlorate

Answer 1

Potassium chloride

Question 2

Predict the colour of the product in the previous question.

Answer 2

White

Question 3

Caesium + water …

Answer 3

caesium hydroxide + hydrogen

Question 4

The melting and the boiling point of halogens become ………………. as we go down the group, and the molecules become ………..

Answer 4

increase, bigger

Question 5

Bromine and iodine are not gaseous, but have low boiling points. This means that they produce vapour at relatively low temperature. They are……

Answer 5

volatile

Question 6

Bromine produces some ,…………..vapour, seen here above the liquid bromine in the jar.

Answer 6

red-brown

Question 7

When iodine is heated gently, it changes directly from a ………… to a …………… without first becoming a liquid

this is called

Answer 7

solid, gas

This is called sublimation.

Question 8

Physical Properties of Halogens

Answer 8

• The boiling points of the halogens increases down the group.
• Fluorine and chlorine are gases at RTP.
• Bromine is a liquid at RTP.
• Iodine is a solid at RTP.

Question 9

The boiling points of the halogens increases down the group 7 (halogens) Explain why

Answer 9

this can be explained because the size of the intermolecular forces down the group increase. This means a higher temperature and more energy is needed to overcome the attractions between molecules to change to the gaseous state.

Question 10

How do halogen molecules exist?

Answer 10

All halogen atoms require one more electron to obtain a full outer shell and become stable.

Each atom can achieve this by sharing one electron with another atom to form a single covalent bond.

diatomic molecules

Question 11

in halogens group

Reactivity ………… up the group.

Answer 11

increases

Question 12

The reactivity of halogens decreases going down the group. What is the reason for this?

Answer 12

• The atoms of each element get larger going down the group.
• This means that the outer shell gets further away from the nucleus and is shielded by more electron shells.
• The further the outer shell is from the positive attraction of the nucleus, the harder it is to attract another electron to complete the outer shell.

Question 13

where does the attraction of halogens for an extra electron gets greater?

Florine ? or clorine ?

Answer 13

going up the group

Question 14

If we mix a metal halide with a more reactive halogen, the electron will be transferred from the ………….to the ………………….reactive halogen:

Answer 14

less , more

Question 15

uses of bromine

uses of chlorine

uses of fluorine

Answer 15

cromine : photography, medicines

chlorine : antiseptics and disinfectants, Bleach to kill bacteria

fluorine: toothpase prevention from decay , polymers, add to water

Question 16

Astatine is below iodine in group 7. Predict, with a reason, which halogens astatine will displace from solutions of their halides.

Answer 16

Astatine will not displace any of the other halogens as reactivity decreases down the group so astatine is the least reactive.

Question 17

As you go down group 7, it becomes more difficult for the atoms to form a negative ion because:

Answer 17

the atoms are getting larger as there are more shells of electrons

so the force of attraction between the positive nucleus and the incoming electron decreases.

Question 18

§the atoms are getting larger as there are more shells of electrons

§

§so the force of attraction between the positive nucleus and the incoming electron decreases.

Answer 18

Iodine atoms are larger than chlorine atoms as they have more shells of electrons.

There is a weaker force of attraction between the positive nucleus and the incoming electron in iodine than in chlorine.

Question 19

Displacement reactions are also …………………reactions.

Answer 19

redox

Oxidation Is Loss of electrons

Reduction Is Gain of electrons

Question 20

Bromine reacts with potassium iodide solution.

Br2 + 2KI → I2 + 2KBr

(a) Write the ionic equation for this reaction.
(b) Write the half equations.
(c) Explain what has been oxidised and what has been reduced.

Answer 20

Answers

(a) Br2 + 2I− → I2 + 2Br−
(b) Br2 + 2e → 2Br−

2I− → I2 + 2e

(c) Bromine molecules have gained electrons so they have been reduced.

Iodide ions have lost electrons so they have been oxidised.

Question 21

• The air is made up mostly of ………………and ……………..along with small amounts of other gases
• Gases of the air can be separated by ……………..

Answer 21

• The air is made up mostly of nitrogen and oxygen along with small amounts of other gases
• Gases of the air can be separated by fractional distillation.

Question 22

The composition of air

Answer 22

• Around 78% of the air is nitrogen.
• About 21% is oxygen.
• The remaining 1% is mostly argon (0.93%), with carbon dioxide (.04%) and varying amounts of water vapour.

Question 23

Nitrogen - 196ºC

Oxygen - 183ºC

Argon - 186ºC

When air is distilled:

1. Which gas will boil first?
2. Which gas will there be most of?
3. Which gas will there be least of?

Answer 23

When air is distilled:

1. Which gas will boil first? Nitrogen
2. Which gas will there be most of? Nitrogen
3. Which gas will there be least of? Argon

Question 24

1. Carbon + oxygen
2. Hydrogen + oxygen

Methane (CH4) + oxygen

Sulfur + Oxygen à Sulfur Dioxide

Write the symbol equation

Answer 24

C + O2 —> CO2

H2 + 1/2 O2 —-> H2O

CH4 + O2 —> CO2 + 2H2O

S + O2——> SO2

SO2 is acid gas

Question 25

is an acid gas that can also dissolve in rainwater and cause acid rain.

It contributes to photochemical smog and is harmful to humans and animals.

Answer 25

NO2

Nitrogen Dioxide

Question 26

Write the combusion equation for Nitrogen and Oxygen

Answer 26

Nitrogen + Oxygen à Nitrogen Dioxide

N + O2 à NO2

Question 27

what do we use for the combustion of nitrogen and oxygen? and why do we need it?

Answer 27

combustion engine

combustion engine temperatures are high enough for the oxygen in the air to combine with the nitrogen:

Question 28

Give 3 causes for the Release of Carbon Dioxide

Answer 28

1. Excess Carbon dioxide can cause a process known as Global Warming.
2. Acid rain can also release carbon dioxide from rocks; acidic oceans can react with rocks or corals that contain calcium carbonate to also release carbon dioxide gas.
3. Carbon dioxide is also stored in the lakes and oceans – an increase in temperature can reduce carbon dioxide’s solubility and it is release into the atmosphere.
4. Carbon dioxide is stored in rocks as carbonates e.g. calcium carbonate.

The carbonates undergo thermal decomposition (breaking down by heating) in many industrial processes

CaCO3 à CaO + CO2

Question 29

explain the reason that the melting points decrease as we go down the group 1

Answer 29

this is because the atoms get bigger as we go down the group. in the metallic lattice the protons are further from the delocalised electrons in caesium than in sodium and therefore there is weaker electrostatic attraction.

Question 30

Nitrogen makes up about 4/5 of the atmosphere.

Oxygen makes up about 1/5 of the atmosphere.

True of false

Answer 30

True

Question 31

explain the method to measure oxgen in air

why do we need to heat the copper?

when do we stop heating?

what do you notice regarding the volume of the air during the experiment?

what is the initial colour of Copper?

what is the colour at the end of the experement?

why did the colour change?

Explain why you waited for the apparatus to cool down after the experiment before reading the volume of air in the syringe.

Answer 31

https://www.youtube.com/watch?v=xAQ3ACUICcY

so the oxygen in the air reacts with the copper.

when the copper color turnes into black

the volume of the air gets smaller

initial is orange, final is black

cupper reacted with oxygen in the air forming copper oxide

the air volume we measured at the start of the experiment was cool air (100cm3) , and in order to have a fair experiment, we need to let the air cool down so we measure the volume of cool air as well.

otherwise the experiment is not fair.

Question 32

colour of

F2

Cl2

Br2

I2

Answer 32

colour of

F2 (gas) Yellow

Cl2 (gas) green

Br2 (Liquid) red brown liquid orange vapour

I2 (solid) grey solid purple vapour

Question 33

halogen means

Answer 33

salt - producing

Question 34

Explain the trend in reactivity in group 7 in terms of electronic configurations

Answer 34

Florine Fl 2,7

Chlorine Cl 2,8,7

Bromine Br 2,8,8,7

Iodine I

Astatine

Question 35

properties of Halogins

Answer 35

the melting and boiling points increase down the group

the intermolecular attraction becomes stronger down the group

the atom gets bigger

poor conductors of heat and electricity

reactirity decreases down the group

they have poisonous vapour

Question 36

hydrogen halides is….

give an example

Answer 36

halogens reacted with hydrogen.

it is a compound formed between hydrogen and a halogen with the formula HX

X is the halogen atom

H₂(g) + Br₂(g) —-> 2HBr(g)

Question 37

why do we have to handle halogens in a fume cupboard?

Answer 37

because they have extremely poisonous vapours

Question 38

hydrogen halides are (Acidic/ Alkaline)?

give an example

Answer 38

Acidic

HCL

Question 39

halogens react with Hydrogen to form………..

halogens react with alkali metals to form …………….

Answer 39

halogens react with Hydrogen to form hydrogen halides (HCL)

halogens react with alkali metals to form salts (NaCl)

Question 40

Hydrogen halides dissolve in water?

Yes / No

Answer 40

yes

Question 41

when halogens react with metals from group 1 and group2 they form …..

Answer 41

ions

Question 42

intermolecular force

Answer 42

force of attraction between covalent molecules much weaker than covalent bonds within the molecules.

Question 43

when Hydrogen chloride is dissolved in water it forms

…………

Question 44

the melting and boiling points increase down the group 7

explain why

Answer 44

the halogens are all covalent molecular substances and the melting and boiling points increase as the relative molecular mass increases. as the relative molecular mass increases the intermolecular forces of attraction become stronger and therefore more energy must be put in to overcome these stronger forces of attraction.

Question 45

covalent bonds are broken when the halogens melt or boil

True / False

Answer 45

False

only intermolecular forces break.

Question 46

write the ionic equation of the reaction of

chlorine and potassium bromide solution

what is the spectator ion in this reaction?

why do we have a spectator ion?

what is the oxidising agent in this reaction?

what is the reducing agent in this reaction?

Answer 46

2Br^- (aq) + Cl2 (aq) —-> 2CL^- (aq) + Br2(aq)

the spectator ion is potassium 2K⁺

we have a spectator ion because the ionic compound when dissolved in water it splits into its ions. and theses metal ions (2K⁺) does not do anything in the reaction.

the oxidising agent is Cl2 because it was reduced in the reaction ( gained electrones)

the reducing agent is Br2 becuase it gave electrones

Question 47

draw cross dot diagram of Nacl

Answer 47

Question 48

redox reactions is…..

Answer 48

oxidation and reduction

Question 49

what is the difference between

Cl2 and 2CL^-

Question 50

The halogens react with non-metals to form simple ………………Structures

Covalent

Ionic

Metallic

Answer 50

Covalent

Question 51

in the reaction between bromine and iodide ions

write the ionic equation with state symbols

write the oxidising agent and the reducing agent

Answer 51

2I^- (aq) + Br₂(aq) —–> 2Br^-(aq) + I₂(aq)

oxidising agent is bromine

reducing agent is Iodine

Question 52

in Halogens the most reactive one is the best oxidising agent (T/F)

in metals the most reactive one is the best reducing agent (T/F)

Answer 52

in Halogens the most reactive one is the best oxidising agent (T)

in metals the most reactive one is the best reducing agent (T)

Question 53

This table shows a summary of the displacement reactions of the halogens: chlorine, bromine and iodine

Answer 53

Question 54

main features of group 7 elements

Answer 54

have diamotic molecules X2

go from gases to liquid to solid as we move down the group

the melting point the boiling points increase down the group

have coloured poisunous vapours the colours of the elements get darker down the group

form compund with the formula Hx when reacted with hydrogen dissolve in water to form acids

form ionic salts with metals and covalent compounds with non-metals

form X- ions in ionic compounds

become less reactive down the group

will displace elements lower down the group from their salts

Question 55

predict the properties of astantine

Answer 55

very dark grey or black

solid at room temprature

diamotic and contain At2 molecules

react with hydrogen forming HAt

dissolve in water forming acid

form a salt with metals NaAt

contain the astatide ion At- in its ionic salt

less reactive than iodine

will be displaced from solutions by iodine

Question 56

draw a dot cross diagram of the molecule formed when chlorine reacts with hydrogen

Question 57

draw a diagram to show the arrangement of electrons in a flourine atom

Question 58

Although the proportion of carbon dioxide is very small, it plays a substantial role in global warming as a greenhouse gas.

Explain

Question 59

Explain why flourine has a lower melting point than chlorine

Answer 59

the halogens are all covalent molecular substances and the melting and boiling points increase as the relative molecular mass increases. as the relative molecular mass increases the intermolecular forces of attraction become stronger and therefore more energy must be put in to overcome these stronger forces of attraction.

Question 60

What is the percentages of composition of air

Answer 60

Oxygen 21%

Nitrogen 78%

CO2 0.04%

argan 0.9%

Question 61

The percentage of oxygen in air can be determined by burning phosphorus in air and measuring the volume change

Answer 61

As the phosphorus burns it uses up the oxygen inside the bell jar and the water level rises

By making careful measurements of water levels before and after the experiment you can determine the percentage of oxygen in the air

Phosphorus is very suitable for this experiment as it burns readily until all the available oxygen is used up

A disadvantage of this experiment is that phosphorus is toxic, so it is hazardous and great care must be taken to handle it safely

Question 62

To determine the percentage of oxygen in air using the oxidation of iron (rusting)

Answer 62

Method:

Firstly, you will need to measure the volume between the final mark on the scale and the tap (stopcock)

Fill the burette with water up to lowest mark, 50.0 mL, and then let it drain into a small measuring cylinder

Measure the volume of water

Add a little water to moisten the inside of the burette

Make sure the tap is closed and sprinkle some iron filings or push a piece of iron wool into the bottom of the burette

Invert the burette into a trough of water and clamp the burette vertically

Note and record the position of the water level

After 3-4 days note the new position of the water level

Results:

Volume occupied between 50 mL & the tap = 3.8 mL

Initial water level = 2.6 mL

Final water level = 12.7 mL

Data Processing:

Initial volume of air = (50.0 + 3.8) - 2.6 = 51.2 mL

Final volume of air = 53.8 - 12.7 = 41.1 mL

Volume of oxygen = 51.2 - 41.1 = 10.1 mL

Percentage of oxygen = (10.1 ÷ 51.2) x 100 = 19.7%

Conclusion:

The oxygen takes up approximately 20% of the air

Question 64

•Type of bonding in iron oxide is ………

Answer 64

ionic bond

Question 65

write the half equation of rusting

Fe losing electrones

O2 gaining electrones

Answer 65

•Fe → Fe3+ + …e-

O2 + e- → O2

Question 66

Explain rusting

Answer 66

•The conditions for rusting of iron are the presence of water and oxygen. Both of these can be found in humid air.

•

•The process is a redox reaction, so the transfer of electrons is involved.

(Think electrochemistry/redox)

•

•Rusting occurs faster if salt water is present.

(Can you think why this is?)

•

•The salt acts as an electrolyte in the water. Ions improve the conductivity, and so electrons transferred more easily

Question 67

Aluminium more reactive than iron, so why does it appear to stay shiny?

Answer 67

•Aluminium is quite reactive, and so quickly reacts with oxygen in the air.

•

•This forms a very thin layer of aluminium oxide on its surface.

•

•This layer is so thin, that it is transparent.

•

•

•The oxide layer is non-porous, and forms a protective barrier that prevents further oxidation (like varnish).

Question 68

methods of rust prevention

Answer 68

• •Paint
• •Oil
• •Plastic coating.
• •Electroplating with less reactive metal, like chromium (or tin)
• •These methods work because they…..
• •
• • create a barrier, preventing water and oxygen from reaching the iron.
• •Sacrificial metals. This is used on ships and oil rigs. A block of a more reactive metal, typically zinc, is attached to the iron structure.
• This metal reacts faster, and releases electrons into the iron, preventing the iron from losing electrons (prevents oxidation).
• Galvanising: the iron is coated in zinc. This acts as a barrier, but if scratched, the zinc acts as a sacrificial metal, so still prevents rusting
• Alloying: Such as stainless steel. This contains other metals, including chromium.
• The stainless steel still corrodes, but the microscopically thin coating of chromium oxide is impermeable (non-porous) so it creates a barrier so thin that it is transparent.
• Cathodic protection: An electrical circuit/battery is used to provide electrons to the iron. preventing the iron from losing electrons.

•

Question 69

Explain why it doesn’t rust after it’s scrached

Answer 69

Before, zinc acts as a barrier, but once scratched, it acts as a sacrificial metal.

Zinc is more reactive than the iron

Reacts with the oxygen and water first.

Zn → Zn2+ + 2e-

This releases electrons from the zinc into the iron structure

Question 70

cathod prevention

Answer 70

•Power supply provides a source of electrons to protect the iron from oxidation

Question 71

Aluminium more reactive than iron, so why does it appear to stay shiny?

Answer 71

Question 72

Explain rusting of Iron

and the write the symbol equation

Answer 72

rusting of Iron

Rusting is a chemical reaction between iron, water and oxygen to form hydrated iron(III)oxide

Oxygen and water must be present for rusting to occur

Rusting is a redox process and it occurs faster in salty water since the presence of sodium chloride speeds up the reaction

Iron + Water + Oxygen → Hydrated Iron(III) Oxide

4Fe (s) + 3O2 (g) + xH2O (l) → 2Fe2O3.xH2O (s)

Question 73

what is galvanizing?

write the ionic equation

Answer 73

Galvanising / Sacrificial protection

Iron can be prevented from rusting making use of metals higher in reactivity than iron

Galvanising is a process where the iron to be protected is coated with a layer of zinc

ZnCO3 is formed when zinc reacts with oxygen and carbon dioxide in the air and protects the iron by the barrier method

If the coating is damaged or scratched, the iron is still protected from rusting because zinc preferentially corrodes as it is higher up the reactivity series than iron

Compared to iron it loses its electrons more readily:

Zn → Zn2+ + 2e–

The iron stays protected as it accepts the electrons released by zinc, remaining in the reduced state and thus it does not undergo oxidation

The electrons donated by the zinc react with hydrogen ions in the water producing hydrogen gas:

2H+ + 2e– → H2

Zinc therefore reacts with oxygen and water and corrodes instead of the iron

Question 74

what is Sacrificial Corrosion

Answer 74

Sacrificial Corrosion

Sacrificial corrosion occurs when a more reactive metal is intentionally allowed to corrode

An example of this occurs with ships’ hulls which sometimes have large blocks of magnesium or magnesium alloys attached

The blocks slowly corrode and provide protection to the hull in the same way the zinc does by pushing electrons onto the iron which prevents it from being reduced to iron(III) ions

Question 75

What is galvanised iron?

Answer 75

It is iron that is coated with a layer of zinc

Question 85

is a substance that can react with acids and neutralise them.

Answer 85

a base

Question 86

how to test for metal and acid reaction?

Answer 86

making a squeaky pop sound. This shows that hydrogen is present.

Question 87

What is seen when a metal reacts with an acid?

Answer 87

Bubbles being produced

The metal getting smaller

Question 88

What are the names of the substances formed in a neutralisation reaction?

Answer 88

Salt and water

Question 89

A salt made from hydrochloric acid will end in ———

A salt made from nitric acid will end in ————

A salt made from sulfuric acid will end in ———–

Answer 89

A salt made from hydrochloric acid will end in chloride

A salt made from nitric acid will end in nitrate

A salt made from sulfuric acid will end in sulfate

Question 90

go to quiz

https://www.bbc.co.uk/bitesize/topics/zn6hvcw/articles/z9gnn9q

Question 91

complete the word equation

magnesium + sulfuric acid —->

Answer 91

magnesium + sulfuric acid → magnesium sulfate + hydrogen

Question 92

complete the equation

Fe + H₂SO₄ → FeSO₄ + —————

Answer 92

Fe + H₂SO₄ → FeSO₄ + H₂

Question 93

go to quiz

https://www.bbc.co.uk/bitesize/topics/zn6hvcw/articles/zvfxxbk

Question 94

complete the word quation

magnesium + copper sulfate → ———+—————-

can this equation be reversed? Why?

Answer 94

magnesium + copper sulfate → copper + magnesium sulfate

no

copper is less reactive than magnesium. Only a more reactive metal will displace a less reactive metal from its compound.

Question 95

what will happen

If bromine is added to a solution of sodium chloride?

Answer 95

No displacement reaction will occur because the bromine is less reactive than the chlorine.

Question 96

What will be produced if magnesium metal is added to a solution of copper sulfate?

Sulfur dioxide, copper and magnesium

Copper plus magnesium sulfate

Copper magnesium plus sulfur

Answer 96

Copper plus magnesium sulfate

Question 97

go to quizz

https://www.bbc.co.uk/bitesize/topics/zypsgk7/articles/z9sptrd

Question 98

when rocks settle in a new location due to erosion.

Answer 98

Deposition

Question 99

a naturally formed solid that is usually made up of one or more types of minerals.

Answer 99

rocks

Question 100

Forms when lava cools and harderns above Earth’s surface.

Answer 100

Extrusive

Question 101

Sediment layers are formed

Answer 101

when particles are compacted or pressed together

Question 102

Contains bubbles-like holes.
SHINY
HARD
MAY HAVE VISIBLE CRYSTALS
FORMED ABOVE OR BELOW EARTH”S SURFACE.

Answer 102

Decription of igneous rocks

Question 103

What does the rate of reaction depend on

Answer 103

the concentration of a reactant
the temperature of at which the reaction takes place
the surface area of the reactant
the addition of a catalyst

Question 104

What does Rates of Reaction mean?

Answer 104

is how fast a reaction occurs

Question 105

What is the effect of increasing the surface area of the solid?

Answer 105

The smaller the piece of the solid, the larger the overall surface area.Thus if you increase the surface area of the solid, there will be more particles of the solid exposed to the other reactant. Hence, there will be more successful collisions per second.

Question 106

The minimum amount of energy needed for the particles to react.

Answer 106

activation energy

Question 107

When iron nail is heated in a blue Bunsen flame it glows red. What happens when iron powder is sprinkled into the same blue Bunsen flame?

Answer 107

The iron powder(iron fillings) immediately burn and produce yellow - orange sparks.

Question 108

How do catalysts increase rates of reactions?

Answer 108

Catalysts work by offering an alternative pathway to lower activation energy. This means that more of the collisions taking place will have the necessary activation energy. Hence there will be more successful collisions per second.

Question 109

how to make a salt?

Answer 109

acid+alkali=salt+water

Question 110

A catalyst provides an alternative reaction pathway that has a ———-activation energy

(lower/ Higher?)

Answer 110

A catalyst provides an alternative reaction pathway that has a lower activation energy