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Why is CaO and CaCO3 used to remove sulphur dioxide from flue gas
Because CaO is a metal oxide so is basic. It reacts with the SO2 in an acid base reaction
What does strontium and barium react with oxygen to form
Strontium/barium peroxide (O-)
What is needed for Magnesium to react with oxygen, and what does it fo
Heat applied to form MgO (white solid)
How does magnesium react with cold water?
Slow reaction to form insoluble layer of magnesium hydroxide (Mg(OH)2)
How does magnesium react with steam (what can be observed)
Forms MgO. A white flame seen and white solid formed.
Why does Mg and H2O make MgO and not Mg(OH)2 as a final product when reacted with steam
When the hydroxide is formed, it undergoes thermal decomposition to form the oxide
What is the trend in reactivity down group 2
Increasing reactivity
What do calcium, strontium and barium react with cold water to form
Hydrogen and a hydroxide
What is the reaction between a group 2 metal oxide with water
Forms a hydroxide (no other products) - colourless solution
What is the reaction between a group 2 metal oxide and a dilute acid
Forms a salt and water (neutralisation/acid base reaction)
How do group 2 metal hydroxides react with a dilute acid
Forms a salt and water (eg Sr(OH)2 + 2HCl → SrCl2 + 2H2O
What is the trend of solubility of group 2 hydroxides down the group
Increasing solubility of hydroxides down the group
What is the trend of solubility of group 2 sulphates down the group
Decreasing solubility down the group (remember barium sulphate is insoluble - used for barium meals for x-rays)
How will the pH of a solution for the hydroxides change down the group and why
pH will increase (more basic) due to increased concentration of OH- ions
What does a CO3²- ion decompose to
O²- ion and CO2 gas
What does an NO3- decompose to
Smaller, stable NO-2 OR O2- and/or O2/NO2
What do group 2 metal carbonates decompose to form
The metal oxide and carbon dioxide gas
Explain the trend in thermal stability of carbonates down a group
the ionic radius of the metal ion increases
Charge density decreases
Polarising power of metal ion/cation decreases
Polarisation of carbonate ion decreases weakening the C-O bond less
Meaning group 1 carbonates are more stable than group 2
And group 2 carbonates get more stable down the group
What is the only unstable group 1 metal carbonate
Lithium
What is the experimental procedure to compare the thermal decomposition of carbonates
heat sample of carbonate and bubble gas through limewater/gas syringe
Fair test (use same flame/distance between sample and flame/volume of limewater/moles of sample)
Record time taken for limewater to go cloudy
What forms when group 2 nitrates undergo thermal decomposition
Metal oxide, nitrogen dioxide and oxygen
How do you know if a group 2 nitrate has decomposed
brown, toxic gas formed (NO2)
Relights a glowing splint (O2)
(White solid before and after - not showing how they decomposed)
What weird observations might be found with magnesium and calcium nitrates and why?
They normally have water of crystallisation so solid may dissolve in its own water - makes a colourless solution before it starts to decompose.
What do most group 1 nitrates (not lithium) decompose to form
Metal nitrate and oxygen
What does lithium nitrate decompose to form
Lithium oxide, nitrogen dioxide and oxygen
Why is lithium nitrate more thermally stable than magnesium nitrate
Mg ion is smaller and more highly charged
Mg ion has more polarising power
Mg ion polarises nitrate ion more
It weakens the N-O bonds in the nitrate ion more
What is the experimental procedure to compare the thermal decomposition of nitrates (+safety precaution)
take equal amounts of solid nitrates in test tubes
Heat equally record time taken to produce brown fumes/relight glowing splint
Safety - use fume cupboard
