Module 3 Chapter 8 Flashcards
What is another name for the group 2 metals
Alkaline earth metals
What are the properties of the group 2 metals
They are reactive metals and don’t occur naturally in their elemental form.
They are usually found in stable compounds —> calcium carbonate
Alkaline properties of the metal hydroxides.
How many electrons do group 2 metals have in their outer shells and what sub shell are they in
they have 2 electrons in the outer shell which are in the s subshell
What is the most common reaction that group 2 metals undergo
A redox reaction
What happens to the group 2 metal in a redox reaction and what happens to the electrons
It is oxidised and loses its two outer shell electrons to form a 2+ ions. Another species will gain the electrons and is reduced so it is regarded as a reducing agent.
What is the reaction between a group 2 metal and oxygen
DRAW IT
What substance is oxidised using oxidation numbers
The group 2 metal is oxidised from 0 to +2
Oxygen is reduced from 0 to -2
What is the reaction between a group 2 metal and water
DRAW IT
In the reaction between a group 2 metal and water what is oxidised and what is reduced
The group 2 metal is oxidised as its oxidation number increases from 0 to +2
Hydrogen is reduced as its oxidation number decreases from +1 to 0
What is the reaction between a group two metal and HCL
DRAW IT
In the reaction between a group two metal and HCL what is oxidised and what is reduced
Mg is oxidised as its oxidation number increases from 0 to +2
Hydrogen is reduced as its oxidation number decreases from +1 to 0
What is the reaction between group 2 metal oxides and water
DRAW IT
What is released and as a result what type of solution forms
OH- ions are released forming an alkaline solution and a metal hydroxide.
What do group 2 elements need to do to react
They react by loosing their 2 outer shell electrons. So two successive ionisation energies need to occur.
What is the trend in reactivity as you go down group 2
As you go down group 2 the reactivity increases this is because less energy is required to remove the 2 electrons as you move down the group.
Why does the ionisation energy decrease as you go down the group
Because the attraction between the nucleus and outer shell electrons decreases. Due to increasing atomic radius and increasing electron shielding.
As you go down the group what happens REDOX
They become better reducing agents.
What does solubility do as you go down the group
It increases down the group
Why does solubility increase as you go down the group
The energy needed to separate the ions decreases as there is an increase in the atomic radius and the force of attraction between the delocalised electrons and metal cations in the lattice decreases.
Why does the solubility for the group 2 metal hydroxides increase as you go down the group
The metal - OH bonds become more polar, so more ionic
Therefore the ions require less energy to separate
As well as this the larger metals can coordinate more water molecules.
What are the group 2 metal hydroxides slightly
They are only slightly soluble in water and if the solution becomes saturated the metal hydroxide will precipitate out into a solid.
As a result of solubility increasing down the group what occurs
There is a greater OH- concentration so as a result it;s more alkaline as you go down the group.
What is the first use of group 2 oxides, hydroxides and carbonates
It is used to neutralise acidic soil in agriculture
It is added to fields by farmers as lime to increase the PH of acidic soils.
Example of the neutralisation of soils reaction
Ca(OH)2 + 2H+ —-> Ca 2+ + 2H2O
What is the second use of group 2 oxides, hydroxides and carbonates
It is used fro acid indigestion
They mainly use magnesium hydroxide and calcium carbonates to neutralise the HCL (stomach acid).
What are the Halogens
They are the elements that are found in Group 17 of the periodic table
What is the trend in boiling points of halogens
The boiling point increases as you go down the group
Why does the boiling points increase as you go down the halogens group
There are more electrons, so stronger induced dipole interactions, so it needs more energy to break the intermolecular forces, this results in a higher boiling point as you go down the group.
What are the colours and states of the different halogens
F2 - pale yellow gas
Cl2 - green gas
Br2 - red-brown liquid
I2 - shiny grey-black crystals
At2 - never seen before
What do all halogens exist as at room temperature and pressure
Diatomic molecules (X2)
What are halogens fund as
They are not found in their elemental form naturally but rather as their halide form in salts.
What is the charge of halide ions and how many electrons do they have in their outer shell
Halogens have 7 electrons in their outer shell and halides have a 1- charge.
What is the trend in reactivity for the halogens
It decreases down the group
Why does reactivity decrease as you go down the group
The atomic radius increases, there are more inner shells so more shielding and as a result there is less nuclear attraction to attract an incoming electrons and therefore reactivity decreases.
What are the halogens one electron short of and what subshells are their electrons in
they are one electron short of the noble gas electron structure
And two of the electrons are in the s subshell and 5 electrons in the p subshell shell in its outer shell
What is the half equation of chlorine becoming chloride and what does this mean
DRAW IT
Chlorine is therefore an oxidising agent as it takes electrons away from other species.
What is a halogen displacement reaction
A solution of a halogen is added to an aqueous solution of other halides. The more reactive halogen will displace the less reactive element in its compound.
What is the displacement reaction between chlorine and potassium bromide and say what is oxidised and reduced using oxidation numbers
What is the colour of the different halogens in solution
Chlorine - pale green
Bromine - Orange
Iodine - brown
What can you do to help identify between bromine and iodine in solution and why
Add cyclohexane and shaking it can make the difference more pronounced as the non-polar halogens dissolve more readily in cyclohexane compared to water.
What is the colour of the different halogens in cyclohexane
Chlorine - pale green
Bromine - Orange
Iodine - purple
What is the table of halogen displacement reactions with the colours produced.
DRAW IT
What is the reaction of chlorine and water
And what type of reaction is it
DRAW IT
It’s a disproportionation reaction, as chlorine is both oxidised and reduced.
What is HClO/ chloric acid used for
it acts as a disinfectant.
What is the reaction between chlorine and sodium hydroxide
What type of reaction is it and show why
DRAW IT
It’s a disproportionation reaction as chlorine is both oxidised and reduced.
What are the benefits and risks of using chlorine
+VE
Kills bacteria
Allows for safe drinking water
-VE
Respiratory irritant
Fatal in high concentrations
Toxic
Linked to cancer
What do halogens react with metals to produce
They react with metals to form salts
Uses of halogens
Bleach
Disinfectant (kills microorganisms) and is used in swimming pools and cleaning products
What is the test for chlorine
Dampen blue litmus paper then hold it near the source of the chlorine, it will turn red and then white
What is the test for halide ins
It’s a precipitation reaction with silver nitrate
Where the halide ions react with silver ions to form silver halides which are insoluble in water.
What is the test for halide ins
It’s a precipitation reaction with silver nitrate
Where the halide ions react with silver ions to form silver halides which are insoluble in water.
How are H-halides made and when dissolved in water what is the PH
The hydrogen and chlorine molecules collide, the covalent bonds in hydrogen and chlorine break.
Covalent bonds form between hydrogen and chlorine
When dissolved in water they form acidic solutions.
What is quantitative analysis
Analysis with numerical results
What is qualitative analysis
Simple observations which can often be carried out quickly on a very small scale.
What is the test for carbonate ions
Add a dilute nitric acid
Bubbles will indicate a carbonate could be present
Bubble the gas through limewater
If the limewater turns cloudy CO2 is present and carbonate ions are too
What is the test for carbonate ions asked on
It is a test based on gases and the principle that carbonates will react with acids to produce carbon dioxide.
What makes the limewater cloudy
A precipitate of calcium carbonate forms making the limewater cloudy
What is the equations for the calcium carbonate precipitate forming
CO2 (g) + Ca(OH)2 (aq) —> CaCO3 (s) + H2O (l)
What is a problem with most sulphates
Most of the sulphates are soluble in water
What are the insoluble sulphate compounds
Lead, barium and calcium sulphates are the only insoluble sulphate compounds.
What is the test for sulphate ions
Add barium nitrate to your sample
If sulphate ions are present a white precipitate will form that sinks to the bottom.
What is the ionic equation for barium sulphates formation
Ba 2+ + SO4 2- —> BaSO4
What are most halides and what is the exception
Most halides are soluble in water however silver halides are insoluble
What is the test for halide ions
First add dilute nitric acid and then add silver nitrate.
What are the different positive results for the halide test
White precipitate - chloride ions
Cream precipitate - bromide ions
Yellow precipitate - iodide ions
How can the test results be more clear
Adding dilute NH3 solution will test for CL- as the white precipitate will dissolve.
If there is no change add concentrated NH3 solution, which will test for Br- the cream precipitate will dissolve.
If the precipitate remains after adding the solution then the ions are iodide.
What is the order that you should carry out the 3 different tests
Carbonate test, sulphate test, halide test
Why this order
As barium carbonate is a precipitate (false positive)
Silver carbonate and silver sulphate are both precipitates ( false positive)
What does ammonium smell like
It smells fishy or like concentrated cleaning products
What can ammonia do so what do u do
Stimulate the tergeminal nerve and causes pain so you have to waft it.
What is the test for ammonium ions
Add sodium hydroxide
then warm gently to evolve the gas and waft it so you can smell it
The gas will also make PH indicator paper blue
What is the ionic equation for the test for ammonium ions
NH4 + (aq) + OH- (aq) —> NH3 (g) + H2O (l)
