group 2 metals Flashcards
what is the trend in atomic radius down group 2?
- decreases
- more electron shells so bigger atoms
what is the trend of 1st ionisation energy down group 2?
- decreases
- atoms get bigger due to more shielding
- outermost electrons are held more weakly as its further away from the nucleus
- weaker attraction from the nucleus to electron in outer shell
what is the trend in melting point down group 2?
- decrease
- weaker metallic bonding as metal ions are biggerso it has a bigger atomic radius
- lower charge density
- distance between the positive ions and delocalised electrons increases
- electrostatic force of attraction forces between the positive ions and the delocalised electrons weaken
what is group 2 reactions with oxygen?
-The group 2 metals will burn in oxygen.
-Mg burns with a bright white flame.
-The MgO appears as a white powder.
- 2 Mg + O2 → 2 MgO
-MgO is a white solid with a high melting point due to its ionic bonding.
what is the trend in reactivity down group 2?
increases
What does magnesium react with in steam to produce? include chemical equation and state
Magnesium oxide and hydrogen
The reaction is represented as Mg(s) + H2O(g) → MgO(s) + H2(g)
What is the appearance of magnesium oxide produced in the reaction with steam?
White powder
What is the chemical equation for magnesium reacting with warm water?
Mg + 2H2O → Mg(OH)2 + H2
How does the reaction of magnesium with warm water compare to its reaction with steam?
The reaction with warm water is much slower and has no flame
What is the general trend in the reactivity of group 2 metals with cold water?
Increasing vigour down the group
What is the product when calcium reacts with cold water? including chemical equation with states
Calcium hydroxide and hydrogen
The reaction is represented as Ca + 2H2O → Ca(OH)2(aq) + H2(g)
What effect do the hydroxides produced by group 2 metals have on water?
They make the water alkaline if soluble
What observable effects occur during the reaction of group 2 metals with water?
- Fizzing (more vigorous down the group)
- The metal dissolving (faster down the group)
- The solution heating up (more down the group)
- White precipitate appearing with calcium (less precipitate with other metals)
True or False: The reaction of magnesium with warm water produces a bright white flame.
False
What is the chemical equation for the reaction of Calcium with cold water?
Ca + 2H2O → Ca(OH)2 (aq) + H2 (g)
What is the reaction of Strontium with cold water?
Sr + 2 H2O (l) → Sr(OH)2 (aq) + H2 (g)
What is the reaction of Barium with cold water?
Ba + 2 H2O (l) → Ba(OH)2 (aq) + H2 (g)
What do the hydroxides produced from group 2 metals in water
Alkaline
True or False: All group 2 metals react with cold water to form alkaline solutions.
True
why is titanium a useful metal?
- its abundant
- has low density
- corrosion resistant
- used to make strong, light alloys for use in aircraft
how is titanium extracted?
by reaction with a more reactive metal e.g. magnesium
why cant titanium be extracted with carbon or by electrolysis?
- cant be extracted by carbon because titanium carbide (TiC) is formed rather than titanium
- titanium cannot be extracted by electrolysis because it has to be very pure
what is the process of titanium extraction?
- TiO2 is converted to TiCl4 (liquid) at 900°C
- The TiCl4 is purified by fractional distillation in an argon atmosphere.
- The Ti is extracted by Mg in an argon atmosphere at 500°C
what is the chemical equation of the displacement reaction between Ti and Mg?
TiCl4 + 2Mg → Ti + 2 MgCl2
why is titanium expensive?
- The expensive cost of the magnesium
- This is a batch process which makes it expensive because the
process is slower (having to fill up and empty reactors takes
time) and requires more labour and the energy is lost when the
reactor is cooled down after stopping - The process is also expensive due to the argon, and the need to
remove moisture (because TiCl4 is susceptible to hydrolysis). - High temperatures required in both steps
how can TiO2 be converted into TiCl4?
it can be purified by fractional distillation,
TiCl4 being molecular (liquid at room temperature) rather than ionic like TiO2
(solid at room temperature).
how can calcium oxide remove SO2 from waste gases from furnaces (e.g. coal fired power stations)?
-by flue gas desulfurisation. The
gases pass through a scrubber containing basic calcium oxide which
reacts with the acidic sulfur dioxide in a neutralisation reaction.
what is the chemical equation to calcium oxide
reacting with the acidic sulfur dioxide in a neutralisation reaction?
SO2 + CaO → CaSO3
- forms calcium sulfite which can be used to make calcium sulfate for plasterboard
what is the trend in solubility down group 2 of hydroxides?
-becomes more soluble down the group
-All Group II hydroxides when not soluble appear as white precipitates.
What is magnesium hydroxide classed as in terms of solubility?
Insoluble in water
What is the simplest ionic equation for the formation of Mg(OH)2?
Mg2+(aq) + 2OH-(aq) → Mg(OH)2 (s)
What is the pH of a suspension of magnesium hydroxide in water?
pH 9
What medical uses does magnesium hydroxide have?
- Neutralise excess acid in the stomach
- Treat constipation
(magnesium hydroxide is suspended as milk of magnesia)
What is the chemical equation of the reaction of magnesium hydroxide with hydrochloric acid?
Mg(OH)2 + 2HCl → MgCl2 + 2H2O
Why is magnesium hydroxide safe to use?
It is weakly alkaline
What is a preferable alternative to using magnesium hydroxide in treating acidity?
Calcium carbonate as it will not produce carbon dioxide gas
What is calcium hydroxide classed as in terms of solubility?
Partially soluble in water
What appearance does calcium hydroxide have when suspended in water?
White precipitate and is used in agriculture to neutralise acidic soils from the acid rain
What is the pH of a suspension of calcium hydroxide in water?
-pH 11
-more alkaline than magnesium hydroxide as it is more soluble so there will be more hydroxide ions present in solution.
What is an aqueous solution of calcium hydroxide commonly called?
Lime water
What test can lime water be used for?
Test for carbon dioxide
What happens when carbon dioxide is bubbled through lime water?
Limewater turns cloudy as white calcium carbonate is produced
What is the chemical equation for the reaction of calcium hydroxide with carbon dioxide?
Ca(OH)2 (aq) + CO2 (g) → CaCO3 (s) + H2O (l)
How does barium hydroxide behave in water?
Easily dissolves
What type of solution does barium hydroxide create?
Strongly alkaline solution
What is the ionic chemical equation of the reaction for the dissolution of barium hydroxide in water?
Ba(OH)2 (s) + aq → Ba2+(aq) + 2OH-(aq)
How does the solubility of sulfates change down the group?
Group II sulfates become less soluble down the group.
Which sulfate is the least soluble?
BaSO4 is the least soluble.
What is the ionic equation for the formation of barium sulfate?
Ba2+(aq) + SO4^2-(aq) → BaSO4(s)
What is the medical use of barium sulfate?
Barium sulfate is used in a ‘Barium meal’ for x-rays of intestines.
Why is barium sulfate safe for use despite barium’s toxicity?
Barium sulfate’s low solubility means it is not absorbed into the blood.
What happens when barium metal reacts with sulfuric acid?
It reacts slowly due to the formation of insoluble barium sulfate.
What is the chemical equation for reaction of barium metal with sulfuric acid?
Ba + H2SO4 → BaSO4 + H2
How does the solubility of sulfates affect reactions with acids?
The same slow reaction effect occurs to a lesser extent with metals going up the group.
What is the reagent used to test for sulfate ions?
Acidified barium chloride solution.
What is observed when acidified barium chloride is added to a solution containing sulfate ions?
A white precipitate of barium sulfate forms.
What is the simplest ionic equation for testing sulfate ions?
Ba2+(aq) + SO4^2-(aq) → BaSO4(s)
Why is hydrochloric acid used in testing for sulfate ions?
To react with carbonate impurities that could form a false positive.
What happens if sulfuric acid is used instead of hydrochloric acid in sulfate testing?
It would give a false positive result due to sulfate ions present.
What is the reaction equation when testing for carbonates?
2HCl + Na2CO3 → 2NaCl + H2O + CO2
What observation indicates the presence of carbonate ions?
Fizzing due to CO2 production.
describe how a student could distinguish between aq solutions of KNO3 and K2SO4 using 1 simple test tube reaction
- reagent : acidified barium chloride solution
- observation with KNO3 is colourless
- observation with K2SO4 is white precipitate
describe how a student could distinguish between aq solutions of MgCl2 and AlCL3 using 1 simple test tube reaction
- reagent: Na(OH)
- observation with MgCL2:white precipitate
- observation with ALCl3: white ppt dissolved in excess Na(OH)
