C9 Flashcards
What is the trend in atomic radius in group 2?
Increase, as each atom going down the group will have an additional electron shell, therefore will have greater shielding which will result in a weaker efa between the valence shell and nucleus meaning it is pulled towards the nucleus less
What is the trend in reactivity down the group 2?
It will increase as you go down the group, each atom will have 1 more electron shell, meaning that each atom has more shielding, resulting in a weaker efa between the nucleus and valence shell, meaning the electron is easier to lose therefore will have an increased reactivity.
What is the trend in ionisation energy in group 2?
Decreases as you go down the group because each atom will have plus 1 electron shells, therefore will have more shielding which means the efa between the nucleus and valence electron is weaker, meaning it will require less energy to ionise.
What is the trend in melting point in group 2?
Decreases down the group because as you go down the group atomic radius increases, meaning in the metallic structure, the larger ions will have to act over a longer distance which will weaken the efa between the positive ions and sea of delocalised electrons.
What type of reaction is a group 2 metal + water?
Redox
What is formed when a group 2 metal reacts with LIQUID water?
An Alkaline solution (metal hydroxide) and hydrogen (H2) gas
What is the balanced symbol reaction for a group 2 metal with LIQUID water, e.g. Mg
Mg + 2H2O —–> Mg(OH)2 + H2
What is Mg(OH)2 commonly used for?
Used in milk of magnesia for treating indigestion as it neutralises stomach acid
What is true about the rate of reaction of a group 2 metal with liquid water?
Reacts very slowly
What is formed when a group 2 metal reacts with STEAM?
A metal oxide (that is a white soluble solid) and hydrogen gas
What is true about the rate of reaction of a group 2 metal with liquid water?
Reacts very fast as the steam provides it with extra energy,
What is the balanced symbol reaction of a group 2 metal with STEAM?
Mg + H2O —-> MgO + H2
What is the common use of Ca(OH)2 in agriculture?
Called Slaked Lime and is used to treat acidic soil, it is used to treat acidic soil.
How and why is titanium extracted?
- TiO2 (solid) is converted to TiCl4 (liquid) at 900C:
- The TiCl4 is purified by fractional distillation in an argon atmosphere.
- The Ti is extracted by Mg from the TiCl4 in an argon atmosphere at 500C through the following reaction:
TiCl4 + 2Mg –> 2MgCl2 + Ti
Why cant Titanium be extracted with Carbon?
As it will form TiC which makes the metal brittle
What is CaO used for?
It is used to remove S02 from flue gases (factory pollutants) to stop it being released into the atmosphere:
CaO + 2H2O + SO2 —> CaSO3 + 2H2O
What is the trend in solubility of the group 2 metal hydroxides?
Increase down the group. (Mg(OH)2 is least)
How soluble is Magnesium hydroxide?
Almost insoluble
How soluble is Calcium hydroxide?
Sparingly Soluble
How soluble is Strontium Hydroxide?
More Soluble
How soluble is Barium Hydroxide?
Dissolves to produce a very alkaline solution:
Ba(OH)2 + aq —-> Ba2+ 2OH-
What is the trend in solubility of the group 2 sulfates?
Decrease down the group (Mg(OH2) the most)
What are the 2 uses of Barium Sulfate?
- As its sulfate is really insoluble, it is used as a medical tracer, that allows internal organs to be imaged.
- It is also used as a test for sulfate ions. The solution is first acidified with HNO3 or HCL to remove any carbonate ions as CO2, This has to be done as BaCO3 also produces a white precipitate. After that a barium chloride solution is then added and if it forms a white precipitate, it will contain sulphate ions:
Ba2+ + SO4- —–> BaSO4(s)
What would you observer from the group 2 metals reacting with water?
- Fizzing (more vigorous down group)
- The metal will dissolve (faster down the group)
- The solution will heat up (more down the group)
Mg Flame Colour
White
Ca Flame Colour
Orange/Red
Sr Flame Colour
Scarlet
Ba Flame Colour
Green
Colour of Mg(OH)2
White
Why is the extraction of titanium expensive?
- Mg is expensive
- Argon in the argon atmosphere is expensive (this step is important to remove moisture as TiCl4 is susceptible to hydrolysis
- High temp is required
- Batch process
Why does an Mg ribbon need to be cleaned off before it reacts?
An Mg ribbon will often have a thin layer of MgO on the outside, this needs to be cleaned off using emery paper as when testing for rates of reaction with an uncleaned ribbon, you will get a false result as both the Mg and MgO will be reacting at different rates.
