Halogens Flashcards
Name the product of the reaction between potassium and chlorine.
Potassium chloride
Potassium oxide
Potassium chlorate
Potassium chloride
Predict the colour of the product in the previous question.
White
Caesium + water …
caesium hydroxide + hydrogen
The melting and the boiling point of halogens become ………………. as we go down the group, and the molecules become ………..
increase, bigger
Bromine and iodine are not gaseous, but have low boiling points. This means that they produce vapour at relatively low temperature. They are……
volatile
Bromine produces some ,…………..vapour, seen here above the liquid bromine in the jar.
red-brown
When iodine is heated gently, it changes directly from a ………… to a …………… without first becoming a liquid
this is called
solid, gas
This is called sublimation.
Physical Properties of Halogens
- 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.
The boiling points of the halogens increases down the group 7 (halogens) Explain why
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.
How do halogen molecules exist?
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
in halogens group
Reactivity ………… up the group.
increases
The reactivity of halogens decreases going down the group. What is the reason for this?
- 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.
where does the attraction of halogens for an extra electron gets greater?
Florine ? or clorine ?
going up the group
If we mix a metal halide with a more reactive halogen, the electron will be transferred from the ………….to the ………………….reactive halogen:
less , more
uses of bromine
uses of chlorine
uses of fluorine
cromine : photography, medicines
chlorine : antiseptics and disinfectants, Bleach to kill bacteria
fluorine: toothpase prevention from decay , polymers, add to water
Astatine is below iodine in group 7. Predict, with a reason, which halogens astatine will displace from solutions of their halides.
Astatine will not displace any of the other halogens as reactivity decreases down the group so astatine is the least reactive.
As you go down group 7, it becomes more difficult for the atoms to form a negative ion because:
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.
§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.
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.
Displacement reactions are also …………………reactions.
redox
Oxidation Is Loss of electrons
Reduction Is Gain of electrons
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.
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.
- The air is made up mostly of ………………and ……………..along with small amounts of other gases
- Gases of the air can be separated by ……………..
- 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.
The composition of air
- 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.
Nitrogen - 196ºC
Oxygen - 183ºC
Argon - 186ºC
When air is distilled:
- Which gas will boil first?
- Which gas will there be most of?
- Which gas will there be least of?
When air is distilled:
- Which gas will boil first? Nitrogen
- Which gas will there be most of? Nitrogen
- Which gas will there be least of? Argon
- Carbon + oxygen
- Hydrogen + oxygen
Methane (CH4) + oxygen
Sulfur + Oxygen à Sulfur Dioxide
Write the symbol equation
C + O2 —> CO2
H2 + 1/2 O2 —-> H2O
CH4 + O2 —> CO2 + 2H2O
S + O2——> SO2
SO2 is acid gas
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.
NO2
Nitrogen Dioxide
Write the combusion equation for Nitrogen and Oxygen
Nitrogen + Oxygen à Nitrogen Dioxide
N + O2 à NO2
what do we use for the combustion of nitrogen and oxygen? and why do we need it?
combustion engine
combustion engine temperatures are high enough for the oxygen in the air to combine with the nitrogen:
Give 3 causes for the Release of Carbon Dioxide
- Excess Carbon dioxide can cause a process known as Global Warming.
- 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.
- 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.
- 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
explain the reason that the melting points decrease as we go down the group 1
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.
Nitrogen makes up about 4/5 of the atmosphere.
Oxygen makes up about 1/5 of the atmosphere.
True of false
True
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.
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.
colour of
F2
Cl2
Br2
I2
colour of
F2 (gas) Yellow
Cl2 (gas) green
Br2 (Liquid) red brown liquid orange vapour
I2 (solid) grey solid purple vapour
halogen means
salt - producing
Explain the trend in reactivity in group 7 in terms of electronic configurations
Florine Fl 2,7
Chlorine Cl 2,8,7
Bromine Br 2,8,8,7
Iodine I
Astatine
properties of Halogins
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
hydrogen halides is….
give an example
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)
why do we have to handle halogens in a fume cupboard?
because they have extremely poisonous vapours
hydrogen halides are (Acidic/ Alkaline)?
give an example
Acidic
HCL
halogens react with Hydrogen to form………..
halogens react with alkali metals to form …………….
halogens react with Hydrogen to form hydrogen halides (HCL)
halogens react with alkali metals to form salts (NaCl)
Hydrogen halides dissolve in water?
Yes / No
yes
when halogens react with metals from group 1 and group2 they form …..
ions
intermolecular force
force of attraction between covalent molecules much weaker than covalent bonds within the molecules.
when Hydrogen chloride is dissolved in water it forms
…………
the melting and boiling points increase down the group 7
explain why
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.
covalent bonds are broken when the halogens melt or boil
True / False
False
only intermolecular forces break.
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?
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
draw cross dot diagram of Nacl
redox reactions is…..
oxidation and reduction
what is the difference between
Cl2 and 2CL-
The halogens react with non-metals to form simple ………………Structures
Covalent
Ionic
Metallic
Covalent
in the reaction between bromine and iodide ions
write the ionic equation with state symbols
write the oxidising agent and the reducing agent
2I- (aq) + Br2(aq) —–> 2Br-(aq) + I2(aq)
oxidising agent is bromine
reducing agent is Iodine
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)
in Halogens the most reactive one is the best oxidising agent (T)
in metals the most reactive one is the best reducing agent (T)
This table shows a summary of the displacement reactions of the halogens: chlorine, bromine and iodine
main features of group 7 elements
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
predict the properties of astantine
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
draw a dot cross diagram of the molecule formed when chlorine reacts with hydrogen
draw a diagram to show the arrangement of electrons in a flourine atom
Although the proportion of carbon dioxide is very small, it plays a substantial role in global warming as a greenhouse gas.
Explain
Explain why flourine has a lower melting point than chlorine
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.
What is the percentages of composition of air
Oxygen 21%
Nitrogen 78%
CO2 0.04%
argan 0.9%
The percentage of oxygen in air can be determined by burning phosphorus in air and measuring the volume change
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
To determine the percentage of oxygen in air using the oxidation of iron (rusting)
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
•Type of bonding in iron oxide is ………
ionic bond
write the half equation of rusting
Fe losing electrones
O2 gaining electrones
•Fe → Fe3+ + …e-
O2 + e- → O2
Explain rusting
•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
Aluminium more reactive than iron, so why does it appear to stay shiny?
•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).
methods of rust prevention
- •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.
•
Explain why it doesn’t rust after it’s scrached
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
cathod prevention
•Power supply provides a source of electrons to protect the iron from oxidation
Aluminium more reactive than iron, so why does it appear to stay shiny?
Explain rusting of Iron
and the write the symbol equation
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)
what is galvanizing?
write the ionic equation
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
what is Sacrificial Corrosion
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
What is galvanised iron?
It is iron that is coated with a layer of zinc
is a substance that can react with acids and neutralise them.
a base
how to test for metal and acid reaction?
making a squeaky pop sound. This shows that hydrogen is present.
What is seen when a metal reacts with an acid?
Bubbles being produced
The metal getting smaller
What are the names of the substances formed in a neutralisation reaction?
Salt and water
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 ———–
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
go to quiz
https://www.bbc.co.uk/bitesize/topics/zn6hvcw/articles/z9gnn9q
complete the word equation
magnesium + sulfuric acid —->
magnesium + sulfuric acid → magnesium sulfate + hydrogen
complete the equation
Fe + H₂SO₄ → FeSO₄ + —————
Fe + H₂SO₄ → FeSO₄ + H₂
go to quiz
https://www.bbc.co.uk/bitesize/topics/zn6hvcw/articles/zvfxxbk
complete the word quation
magnesium + copper sulfate → ———+—————-
can this equation be reversed? Why?
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.
what will happen
If bromine is added to a solution of sodium chloride?
No displacement reaction will occur because the bromine is less reactive than the chlorine.
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
Copper plus magnesium sulfate
go to quizz
https://www.bbc.co.uk/bitesize/topics/zypsgk7/articles/z9sptrd
when rocks settle in a new location due to erosion.
Deposition
a naturally formed solid that is usually made up of one or more types of minerals.
rocks
Forms when lava cools and harderns above Earth’s surface.
Extrusive
Sediment layers are formed
when particles are compacted or pressed together
Contains bubbles-like holes.
SHINY
HARD
MAY HAVE VISIBLE CRYSTALS
FORMED ABOVE OR BELOW EARTH”S SURFACE.
Decription of igneous rocks
What does the rate of reaction depend on
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
What does Rates of Reaction mean?
is how fast a reaction occurs
What is the effect of increasing the surface area of the solid?
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.
The minimum amount of energy needed for the particles to react.
activation energy
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?
The iron powder(iron fillings) immediately burn and produce yellow - orange sparks.
How do catalysts increase rates of reactions?
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.
how to make a salt?
acid+alkali=salt+water
A catalyst provides an alternative reaction pathway that has a ———-activation energy
(lower/ Higher?)
A catalyst provides an alternative reaction pathway that has a lower activation energy
