Y1 Periodicity (I) Flashcards
How does the melting point of group 2 change down the group?
Melting point decreases down the group
- same charge
- atoms are much larger
- specific charge is smaller as charge is more diluted
- so less energy to break bonds
How does the pH of group 2 hydroxides change down the group?
pH increases down the group
- down group 2 atoms become larger
- more OH- ions per size ratio at the top of the group
- top ofthe group are better reductants
Group 2 hydroxides, which are better reductants?
Top of the group
Where is atomic radius the greatest?
bottom left of the periodic table
- (across) less protons, less nuclear charge
- (down) more shielding, outermost electron is further from the nucleus
Where is ionisation energy the greatest?
top right of the periodic table
Where is electronegativity the greatest?
top right of the periodic table
Reactivity of group two down the group?
Increases
Mg + steam
product: MgO + H2
instead of Mg(OH)2 +H2
reacts more vigorously with steam
Where are group 2 hydroxides more soluble?
Bottom of the group
Where are group 2 sulfates more soluble?
Top of the group
sulfate ion test explained
-add BaCl2 or Ba(NO)3 aqueous
- will form a white ppt when BaSO4(s) is formed
-Problem if CO3(2-) ions are present as will form also white BaCO3(s)
-either test for carbonates with dilute nitric acid (bubble through limewater will turn limewater cloudy) or add HCl to remove with effervescence
Sulfate ion test
- Add HCl to remove and carbonate (CO3(2-)) or sulfite (SO2(2-))impurities
-Add barium chloride solution - positive test if white ppt formed
Cabonate ion test
-Add HCl (or any acid)
- effervesence produced
- bubble through limewater
-positive result if limewater turns cloudy
Carbonate ion + acid
salt + carbon dioxide + water
Halide ion test
- Add nitric acid to remove and carbonate (CO3(2-)) or sulfite (SO2(2-))impurities
-Add silver nitrate
silver chloride - white ppt
silver bromide - cream ppt
silver iodide - yellow ppt
Silver nitrate test, tests for?
Halide ions
Barium chloride test, tests for?
Sulfates
Milk of magnesia is?
-Magnesium hydroxide Mg(OH)2
-Helps in digestion as it contains a suspension of the insoluble hydroxide (hence harmless)
-Neutralises the stomache acid and helps indigestion
What do you neutralise acidic soils with?
-Calcium hydroxide
-Ca(OH)2 + 2(H+) –> 2H20 + Ca(2+)
-H+ is acid
How do you neutralise flue gases?
- Have CaO or CaCO3 filter beds in the flue columns
- SO2 + CaO –> CaSO3 (IV)
- SO2 + CaCO3 –> CaSO3 + CO2
-the two compounds are known as lime and limestone - a slurry is a mixture of lime limestone and water
How would you describe group 2 elements?
Alkaline earth metals
kwjssn
what is calcium hydroxide known as?
slaked lime
The group two elements
beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
What is a barium meal?
-Used in medicine
-a patient will swallow a cup of barium sulfate (s)
- the compund is opaque to xrays and so a structure of the persons digestive system will be able to be produced.