2.2 group 2 notes Flashcards
what are group 2 MP like
high
why are group 2 MP high
metals have strong metallic bnding
are group one or group 2 harder
group 2 are harder and have a higher density than group one elements
why are group 2 elements harder and have a higher density than group 1 elements
ions are smaller and more highly charged therefore ions pack together more closely leading to stronger bonding
what are group 2 elements reactivity’s like
reactive with similar chemical reactions
why are group 2 elements reactive metals with similar chemical reactions
they all lose 2 electrons when they react
appearance of group 2 compounds
white solids/colourless solutions
trend in atomic radius in group 2
increases down group 2
why does atomic radius increase down group 2
shells increase
shielding increases
nuclear attraction on outer electrons decreases
trend in first IE down group 2
decreases
why does first IE decrease down group 2
shells increase
shielding increases
nuclear attraction on outer electrons decreases
trend in melting points down group 2
decrease
why do melting points decrease down group 2
- ions all have 2+ charge but increase in size
- as ions increase, charge density decreases- attraction/bonding decreases
trend in reactivity down group 2
increases
why does reactivity increase down group 2
lose electrons more readily as we go down group because:
- ions all have 2+ charge but increase in size
- as ions increase, charge density decreases- attraction/bonding decreases
observations of the reaction of magnesium with cold water
very slow
few bubbles of gas
products of the reaction of magnesium with cold water
magnesium hydroxide and hydrogen
Products of the reaction of magnesium with steam
Magnesium oxide and hydrogen
Observations of the reaction between calcium and water
Effervescence
Solid Ca dissolves
Products of the reaction between calcium and water
Calcium hydroxide and hydrogen
Observations of the reaction between strontium and water
Vigorous fizzing
Solid strontium dissolves
Products of reaction between strontium and water
Strontium hydroxide and hydrogen
Observations of reaction between barium and water
- even more vigorous fizzing
- solid barium dissolves
Products of the reaction between barium and cold water
Barium hydroxide and hydrogen
What is the general trend in reactivity with water of group 2 element as you go down the group
Reactivity increases
Why is titanium a useful metal
Strong, high melting point and high corrosion resistance
Where does titanium have many applications
In the aerospace, marine and motor vehicle industries
Why is it difficult to extract titanium from its ores
Because reduction with carbon produces a brittle titanium carbide
How is the production of titanium carbide avoided in the extraction of titanium from its ore
The titanium oxide ore is first reacted with chlorine and carbon to form titanium chloride
What happens to the titanium chloride to produce titanium
It is reduced with magnesium to produce titanium
What are group 2 hydroxides
Bases
What do group 2 hydroxides react with
Acids
Example of acid base reaction between magnesium hydroxide and hydrochloric acid
Mg(OH)2 + 2HCL > MgCl2 + 2H20
What is magnesium hydroxides solubility like and pH of the solution it makes
V sparingly soluble
PH 8-9
What is calcium hydroxides solubility like and pH of the solution it makes
Not much better than magnesium
pH 10-11
What is strontium hydroxides solubility like and pH of the solution it makes
Relatively soluble, pH 11-12
What is barium hydroxides solubility like and pH of the solution it makes
Pretty soluble, pH 12-14
What the trend in water solubility of group 2 hydroxides
Increases down the group
What is the trend in pH of resultant solutions from reaction of group 2 hydroxides and acids
Increases down the group
How are relative solubilities of group 2 hydroxides tested
Adding aqueous sodium hydroxide to the solutions of group 2 ions and observing the precipitate formed
What indicates that magnesium hydroxide is sparingly soluble
The pH of the solution is slightly alkaline, indicating a small amount of hydroxide ions have dissolved- hence a thick white precipitate will be seen
How is it indicated that barium hydroxide is more soluble than magnesium hydroxide
Very thin white PPT seen
What is magnesium hydroxide used for
In medicine
Milk of magnesium
Indigestion medicine- neutralises stomach acid
How is calcium hydroxide used
To neutralise acidic soil
Obtained from limestone- cheap
What is the trend in solubility of group 2 sulfates
Decreases down the group
What are calcium and barium sulfates’ solubility like
Calcium- sparingly soluble
Barium- insoluble
How to test the relative solubility of group 2 sulfates
Add sulfuric acid/aqueous sodium sulfates to solutions of group 2 ions and observing the precipitates formed
What is magnesium sulfate solubility and how would this be seen
Soluble- no precipitate
What is barium sulfate solubility and how would this be seen
Insoluble so a thick white precipitate would be seen
What can the solubilities of group 2 hydroxides and sulfates be used to test
The identity of group 2 ions in solution
Uses of barium salts
Tests for sulfates
Method for using barium salts to test for sulfates
- add to 1cm3 unknown solution
- add HCl
- add 1cm3 BaCl2(aq)
Interpretation for using barium salts to test for sulfates
White PPT? Sulfate ions present
Equation for using barium salts to test for sulfates
BaCl2 + Na2SO4 > BaSO4 + 2NaCl
Uses of barium sulfate
Medicine
Barium meal
BaSO4- good at absorbing xrays- if ingested provides a good image of the digestive tract via X-ray images
Why is using barium sulfate in medicine harmless despite it being toxic
Barium sulfate is insoluble so barium ions are not absorbed into the blood
Uses of calcium compounds
CaO or CaCO3 can be used to remove sulfur dioxide from flue gas
Equation of neutralisation of sulfur dioxide using calcium oxide
CaO + SO2 > CaSO3
Equation for reaction of calcium carbonate with so2
CaCO3 + SO2 > CaSO3 + CO2
