Topic 4 Flashcards
(57 cards)
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 of metal carbonate
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
