Group 2 And 7 Flashcards
What happens to melting point down group 2
Melting point generally decreases except with mg
Because metallic bonding gets weaker (size if metal ion increases)
What do group 2 metals form when reacting with water
Metal hydroxide and hydrogen gas
What is the reaction of magnesium with water vs steam
Reacts very slowly with cold water to form magnesium hydroxide
Readily reacts with steam to form magnesium oxide
How do the rest do group 2 metals react with water as you go down?
All react with cold water to from hydroxides
Vigorous reaction increases down the group
Why does reactivity of group 2 metals increase down the group
It is successively easier to remove electrons to form the 2+ ion
(Atomic radius increases)
What is the trend in solubility do group 2 metal hydroxides down the group
What does this results in
Increases
So higher ph cos more hydroxide ions
How do you test for mg ions and ca ions
They are sparingly soluble so react magnesium chloride or calcium chloride with sodium hydorxide to form a white precipitate
What type of reaction is it when group 2 metal hydroxides react with acids
Neutralisation
What is a use of magnesium hydroxide
Relieve acid indigestion
Laxative
What is a use of calcium hydroxide
What’s another name for it
Raise the ph of soils in agriculture
Slaked lime
How do you test for ammonia gas
What is reaction between ammonium ions and oh minus ions
Form ammonia gas and water
Damp red litmus paper turns blue
What is the trend in solubility of group 2 metal sulfates
Solubility decreases down the group
What is the chemical test for SO4 2- ions
Colourless solution of sodium sulfate, add barium chloride to form barium sulfate (white precipitate)
Why does barium chloride need to be acidified first
To remove any other ions that could cause a false positive
How is Barium Sulfate used in medicine
Barium meal
To examine a patients digestive system, the mixture containing barium sulfate coats the inner lining of intestines
Why is is safe to have a barium meal i if barium ions are so toxic
Barium sulfate has a very low solubility so hardly any barium ions present in the solution and can’t dissolve into blood etc
How is titanium extracted
Reacting titanium chloride with magnesium
What are the 2 most useful properties of titanium
Corrosion resistant
High strength to weight ratio
What are uses of calcium carbonate and calcium oxide
Neutralise sulfur dioxide present in flue gas
Flue gas desulfurisation
What is the trend in electro negativity of group 7 elements down the group
Electronegativity decreases
What is the trend in boiling points down group 7
Boiling point increases
More electrons so stronger van der waals forces
What happens when halogens act as oxidising agents
They gain electrons to become halide ions
What is the trend in oxidising abilities as you go down group 7
And why
The halogens decrease in oxidising ability
The ability to gain electrons reduces down the group
What type do reactions are halogen displacement reactions
They are redox reactions
What is the role of the halogen in halogen halide displacement reactions
Oxidising agent
What are 2 disproportionation reactions that chlorine can do
React with water
React with cold sodium hydroxide
Define disproportionation reaction
A reaction in which the same element is simultaneously oxidised and reduces
How is chlorine used in water supplies
Used to purify water supplies as it is toxic to bacteria
Added to swimming pools too
What are 2 risk of using chlorine in water supplies
What is the compromise of this
Chlorine is toxic to humans so risk associated with chlorination leaks
Risk of forming chlorinated hydrocarbons
Sufficient chlorine added to kill bacteria but not enough to harm humans
What is another reaction of chlorine
Chlorine reacts with in direct sunlight to produce hydrogen chlorine and oxygen
What is formed when chlorine reacts with cold aqueous sodium hydroxide
Sodium chlorate
(NaOCl)
Household bleach
Sodium chloride and water are 2 other products
What is the trend in reducing ability of halide ions down the group
And why
Reducing ability increases
Ability of halide ion to lose electron increases
What are the stages of a halide ion reacting with concentrated sulfuric acid
Stage 1 is displacement
The halide ions reacts with sulfuric acid (which act as a proton donor)
Stage 2 is redox
With bromides and iodides a redox reaction occurs between concentrated sulfuric acid and halide ion
Chloride and fluoride aren’t good enough reducing agents to react
What do bromide ions reduce sulfuric acid to
Sulfur dioxide
What do iodide ions reduce sulfuric acid to
They reduce sulfuric acid to sulfur dioxide, sulfur and hydrogen sulfur
What is the test for identifying halide ions
What is the exception of this
React them with acidified silver nitrate solution to produce a silver halide precipitate
Silver fluoride (it is soluble so won’t form a precipitate)
Why do you add nitric acid before adding silver nitrate solution
To get rid of any soluble impurities like carbonate and hydroxide ions.
They’d give a false positive
What is the colour of fluorine
Pale yellow gas
What is the colour of chlorine
Green gas
What is the colour of bromine
Red / brown liquid
What is the colour of iodine
Grey solid
Define oxidising ability
The power to take electrons
What is an oxidising agent
Electron acceptor
What colour solution forms when chlorine dispatches bromine ions and iodide ions
Bromine- orange / yellow solution
Iodide - brown solution
What is the colour of precipitates when AgCl, AgBr and AgI are formed
Cl - white
Br - cream
I - yellow
How do you test if the precipitate is cream or white
Add dilute ammonia solution to the AgCl, AgBr and AgI
With cl it dissolves
With br it won’t
With with Ai it won’t
It = precipitate
How do you further test the precipitates
Add concentrated ammonia solution
AgBr - should dissolve
AgI - won’t dissolve
What is reducing power
Ability to donate electrons
What happens when sodium halides react with concentrated sulfuric acid
Misty white fumes produced
(NaHSO4)
What colour is solid sulfur
Yellow
How do you detect hydrogen sulfide
(H2S)
Bad egg smell
