TOPIC 4
group 2 metal + oxygen → - ACCURATE ANSWERS solid white oxide
group 2 metal + chlorine → - ACCURATE ANSWERS solid white chloride
CaCl₂ + 2OH- → - ACCURATE ANSWERS Ca(OH)₂
white precipitate
What colour will a solution turn if bromine is displaced? - ACCURATE ANSWERS ...
group 2 metal + oxygen → - ACCURATE ANSWERS✔✔ solid white
oxide
group 2 metal + chlorine → - ACCURATE ANSWERS✔✔ solid white
chloride
CaCl₂ + 2OH- → - ACCURATE ANSWERS✔✔ Ca(OH)₂
white precipitate
,What colour will a solution turn if bromine is displaced? - ACCURATE
ANSWERS✔✔ Orange
If hexane added red
If an organic solvent, eg. hexane added, the halogen present will dissolve
and form a distinct layer above the aqueous solution.
What colour will a solution turn if iodine is displaced? - ACCURATE
ANSWERS✔✔ Brown
If hexane added purple
If silver nitrate is added to silver halides, what precipitates will form? -
ACCURATE ANSWERS✔✔ Fluoride - no precipitate
Chloride - white
Bromide - cream
Iodide - yellow
What happens when ammonia solution is added - ACCURATE
ANSWERS✔✔ AgCl - precipitate dissolves in dilute ammonia
AgBr - dissolves in conc. ammonia
AgI - precipitate does not dissolve in either
Outline a reaction to identify carbonates and hydrogencarbonates -
ACCURATE ANSWERS✔✔ - add dilute HCl
- both will fizz as carbon dioxide is produced
,- test for carbon dioxide with limewater
Outline a reaction to identify sulfate ions - ACCURATE ANSWERS✔✔
- add dilute HCl to remove any carbonate ions
- add barium chloride
- if a white precipitate of barium sulfate forms, it means the original
compound contained sulfate ions
Outline a reaction to identify ammonium ions - ACCURATE
ANSWERS✔✔ - add NaOH and gently heat
- if ammonia given off, it will turn damp red litmus paper blue
A compound of calcium (A) has water added and solution (B) is formed.
Solution (B) turns cloudy when carbon dioxide is passed through it. The
cloudiness is due to the formation of precipitate (C). Addition of excess
carbon dioxide will remove the cloudiness and (D) will be formed.
Identify the compounds. [4 marks] - ACCURATE ANSWERS✔✔ A -
CaO
B - Ca(OH)₂
C - CaCO₃
D - Ca(HCO₃)₂
Why does the cloudiness disappear in the last step? - ACCURATE
ANSWERS✔✔ Ca(HCO₃)₂ is soluble in water
, The presence of a carbonate ion is usually confirmed using a simple test
carried out in two stages at room temperature. Describe this test and its
results. [2 marks] - ACCURATE ANSWERS✔✔ add HCl
carbon dioxide produced turned lime water cloudy
What is limewater? - ACCURATE ANSWERS✔✔ calcium hydroxide
Ca(OH)₂
When a flame test is carried out on two group 2 carbonates, A gives no
colour and B gives a yellow-red flame. Give the formulae of the metal
ions in A and B. [2 marks] - ACCURATE ANSWERS✔✔ A - Mg²⁺
B - Ca²⁺
Explain the origin of the flame colour and suggest why compound A
produces no flame colour. [4 marks] - ACCURATE ANSWERS✔✔ -
electrons promoted to a higher energy level
- promoted electrons return to their ground state
- emitting light
- for Mg²⁺, the emitted radiation is not in the visible region of the
spectrum
BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl
This reaction is used to test for sulfate ions. Why is dilute HCl added
with the BaCl₂ solution in this test? [1 mark] - ACCURATE
ANSWERS✔✔ to prevent formation of the carbonate
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