Topic 4 Flashcards
What happens to 1st ionisation energy down group 2 and why
Outer electron is held more weakly as more shells so further from nucleus outer electrons are more shielded from nucleus and so easier removed so ionisation decreases down group
What happens to melting points for group 2 down group
Decreases down group as metallic bonding weakens as atomic size increases the distance between the positive ions and delocalised sea of electrons increases so electrostatic force of attraction decreases and less energy is required to overcome bonding
What happens to reactivity down group 2
Increases as atomic radius increases and there is more shielding ,nuclear attraction decreases so it’s easier for outer electrons to be lost and from positive ions
Magnesium in oxygen with burning and without
Mg burns with bright white flame in oxygen and forms white solid MgO
Without burning it reacts slowly with no flame and mgO will form on surface
2mg+02=2mgO
Why must the thin layer of MgO be removed by emery paper before reactions using mg ribbon
Unclean mg would give a false result if testing for something like rates of reaction as MgO reacts at a different rate to Mg
Do group 2 metals react with chlorine
Yes mg +cl2 = mgcl2
What is the reaction for a group 2 metal and steam
Metal + steam = metal oxide + hydrogen
Mg +H2O = MgO + H2
Mg reacts in warm water to produce what
A magnesium hydroxide product
Mg +2H2O= mg(OH)2 +H2
Metal + water gives metal hydroxide
No flame and reacts slower than in steam
What do the hydroxides that from when metal reacts with water do to the ph and what observations can be seen through the reaction down the group 2 metals, and for calcium specifically
Makes it more alkali ,fizzing gets more vigorous down group,heating of water more down group,metal dissolves faster down group,calcium white precipitate formed, less precipitate forms down group going down group gets more soluble do calcium will raise the ph higher than mg
What do group 2 ionic oxides react with water to form,and explain solubility of group 2 metal oxides down the group and what effect this has on PH
Metal Hydroxides
MgO + H2O= mg(OH)2 ph 9
Magnesium hydroxide forms here which is slightly soluble in water so only a small amount dissolves to releases OH- ions higher in the ph , going down group 2 metal oxides are more soluble so ph gets higher
Reaction of group 2 metal oxides and acid
Group 2 metal oxides and acid gives a salt plus water
Reaction of group 2 metal hydroxide plus acids
Group 2 metal hydroxide plus acid gives a salt plus water,
What do group 2 hydroxides appear as when insoluble
White precipitate
What is magnesium hydroxide used in (application) why is it better to use calcium c hydroxide
Used in medicine to neutralise excess acid in stomach ,treat constipation,safe to use as weakly alkaline ,better to use calcium hydroxide as it won’t produce c02 when reacting with acid it’s relatively soluble in water and is used in agriculture to neutralise acidic soils
Explain what lime water is and what it tests for
It’s an aqueous solution of calcium hydroxide tests for co2 which turns cloudy as white calcium carbonate forms when they react.
What is the trend down the group for group 2 sulfates , how is this different for nitric acid and Hcl
Group 2 sulfates become less soluble down the group so Baso4 is the least soluble if barium reacts with sulfuric acid it reacts slowly and insoluble barium
Sulfates produces covering the surface of the metal acting as a barrier to further attack this happens to a lower extent with the other metals in the group, this won’t happen with nitric hydrochloric acid
Ba + H2So4= baSo4 + H2
Metal plus acid gives salt plus hydrogen (redox)
What do group 2 carbonates decompose to produce
Group 2 carbonates decompose to produce group 2 oxides and carbon dioxide gas
MgCo3 = MgO + co2
Thermal decomposition meaning
Use of heat to break down reactant into more than one product
Trend of thermal decomposition down group 2 for metal carbonates ?
Ease of thermal decomposition decreases down group 2 thermal stability is more stable down group as down group cations get bigger have less of a polarising effect and dissort the carbonate ion less , so the c-o bond is not as weakened down the group so it breaks down less easier , so because polarisation deacreases down group thermal decomposition also decreases in ease
Do group 1 metal carbonates decompose
No with the exception of lithium as only have one plus charges so don’t have enough charge density to polarise the carbonate ion Li decomposes in the same way as group one metal carbonates, as its small enough to have polarising effect
Experiment to work out the ease of thermal decomposition
Heat known mass of metal carbonate in side arm boiling tube and pass the gas through limewater ,repeat for different carbonates use same mass of carbonate volume of limewater, time taken for limewater to go cloudy indicates ease of decomposition
Thermal decomposition of group 2 nitrates,state observations ( explanation for thermal stability is same as for metal carbonates)
Group 2 nitrates decompose thermally to produce group 2 oxides and nitrogen gas and oxygen gas, brown gas n2 would be observed , the white nitrate would seen to melt into a colourless solution and re solidify , Li is the only group one metal nitrate that decomposes in the same way as group 2 due to its small size and polarising effect.
2mg (No3)2 = 2mgo + 4No2 + o2
Why would magnesium nitrate decompose thermally easiest
Mg is the smallest has the greater charge density so most polarisation of the nitrate bond N-O bond
How would I set up flame test for group 1&2 metals
Use nichrome metal wire (unreactive won’t give any flame colour) clean by dipping wire into Hcl , heat with Bunsen burner , grind up sample if not powdered dip wire into solid put onto Bunsen and observe flame
Explain the occurrence for a flame when metal reacts with fire
Heat causes electrons to move to higher energy level making it unstable , so it drops back down energy level ,when this happens energy is emitted in the form of visible light energy ,with the wavelength of the observed light
What is the colour of the flame for different group one megals
Lithium - scarlet red
Sodium-yellow
Potassium- lilac
Rubidium -red
Caesium -blue
What is the colour of the flame for different group 2 metals
Magnesium - no colour energy emitted of wavelength outside visible light spectrum
Calcium - brick red
Strontium - red
Barium - apple green
Colours of halogens
Fl2 - very pale yellow very reactive gas
Cl2 - greenish reactive gas ,poisonous in high concentrations
Br2 - red liquid ,gives of dense brown orange poisonous fumes, I2 shiny grey solid sublimes to purple gas
Trend in melting and boiling for group seven
Increases down the group as molecules become larger and have more electrons ,so larger London forces between molecules more energy required to break intermolecular forces.
What is the trend in electronegativity group seven
Deacreases down group As atomic radius increases due to increases number of shells ,nucleus is less able to attract bonding pair
Reactivity of halogens trend
Decreases down the group as atoms get larger more shielding less easier to attract and accept electrons to form -1 ions
Explain oxidation reactions of halide ions by halogens
A halogen that is a strong oxidising agent will displace a halogen that has lower oxidising power from its compound, a more reactive halogen is a stronger oxidising agent so oxidising agent power deacreases down group .
Observing aqueous solutions show what free halogen is present in a displacement reaction ,the free halogen is the less reactive one ,what are the colours
Chlorine - colourless or pale green
Bromine- yellow
Iodine - brown or black solid
The colour of the organic solvent layer in the test tube also shows what fee halogen is present in solution. What are these colour
Chlorine -colourless
Bromine -yellow
Iodine -purple
What can be added to make halogen colour clearer In displacement reactions
Organic solvents e.g hexane
What happens in oxidation reactions between metals and halogens
The metal is oxidised and halogen is reduced
How does chlorine and bromine have an effect on Fe2+ as strong oxidising agents in comparison to iodine
Chlorine and bromine can oxidise Fe 2+ to Fe3+ iodine is not strong enough as an oxidising agent so does the reverse reaction
Cl2 + Fe2+ = 2cl - + Fe3+
2i- + Fe3+= i2 + Fe 2+
What happens when chlorine is added to water and what happens if I add universal indicator after
Chlorine is both oxidised and reduced goes from oxidation state of 0 to -1&1
Cl2+ H2O= HclO +Hcl When universal inductor is added the solution turns red first due to the acidity of chlorine reaction products it then turns colourless as HclO bleaches the colour
What is chlorine water used for
Kill bacteria,treat water,the benefits of chlorine water on health outweigh the toxic effects
Do halogens react in cold dilute NAOH solution what are these products used for (application)
Yes in aqueous NAOH the colour of the halogen solution turns colourless
Cl2 + 2 NAOH = Nacl + Naclo + H20
The mixture of Nacl and Naclo is used as bleach to disinfect and kill bacteria
What is the difference when halogen reacts with cold dilute NAOH solution vs hot
Disproportionation occurs in both but that halogen is oxidised to a higher oxidation state
How does the power of reducing agent change down group seven
Increases power down group as ions get larger it’s easier for outer electrons to be lost
How can the increasing reducing power of group seven be demonstrated
Using sulfuric acid on halogens check book,the ability of bromine to reduce sulfur rather than chlorine and fluorine as down the group power of reducing agent increases
How would I prepare the test to identify which halogen is present using silver nitrate
The test solution is made acidic with nitric acid so that it will react with any carbonates present to prevent the formation of silver carbonate forming that mask observations that are desired, silver nitrate solution is then added dropwise
How does the silver nitrate reaction with halide ions show which halide ion is present in sample
Based on precipitate formed
Fluorides = no precipitate
Chlorides =white precipitate Agcl
Bromides = cream precipitate AgBr
Iodides = pale yellow precipitate AgI
What is the effect of light on silver halides
The precipitates excep AgI , darken In sunlight forming silver metal this reaction is used in photography to form dark bits on film,
Do silver halides react with ammonia
Silver chloride dissolves in dilute ammonia to form a complex ion this solution is colourless
Silver bromide dissolves in concentrated ammonia to form a complex ion also colourless solution
Silver iodide doesn’t dissolve in ammonia as it’s too insoluble
How can hydrogen halides be produced using sodium halide salts and phosphoric acid
Reaction of solid sodium halide salts and phosphoric acid produced hydrogen halides
What are the observations when phosphoric acid reacts with sodium halide salts to produce a hydrogen halide
White steamy fumes of hydrogen halide
They are produced when the Hcl mixes with air because it dissolved the moisture of the air
Why is phosphoric acid more suitable for producing hydrogen halides than sulfuric acid
Phosphoric acid is not an oxidising agent like sulfuric acid so won’t oxidise HBr and HI ,so no extra redox taking place and no other unwanted side products
Explain the apparatus for the reaction of solid sodium halides salts with phosphoric acid to produce hydrogen halides
Tee tube to contain reaction
A delivery tube connected to direct the gas safely
Downwards delivery is used as hydrogen halides are denser than air so will just sink
Are all hydrogen halides soluble in water
Yes they dissolve to form acidic solutions
Do all hydrogen halides react with ammonia
Yes they all react with ammonia to give off white smoke of the ammonium halide
This can be used to test for the presence of hydrogen halides in a sample of when reacted with ammonia to give these results
How do you test for the presence of carbonate ions
Add acid to sample if carbonate CO3^2- is present or hydrogen carbonate HCO3^- then carbon dioxide will be produced which causes fizzing or bubbling to test co2 use limewater
What do carbonates form when reacting with acid
Carbonates when reacting with acids form salt water and carbon dioxide this reaction is the same for hydrogen carbonates except only one H+ is needed for reaction
How can I test for the presence of a sulfate , why does my solution need to be acidified and why can’t I used sulfuric acid to acidify it?
Using acidified BaCl2 when added to a solution that contains sulfate ions a white precipitate forms the acidic solution is to remove carbonates in the sample that could react with Ba 2+ to form barium carbonate which is also a white precipitate ,note sulfuric acid can’t be used to acidify solution as it already has sulfate ions and barium sulfate would produce
How can I test for ammonium ions NH4+ and how can I confirm this test
If a solution contains NH4+ ions adding warm NAOH solution will form NH3(ammonia gas) and water to confirm NH3 use damp litmus paper the red will turn blue as NH3 is alkaline ,NH3 also has a pungent smell
