Group 2, the alkaline earth metals Flashcards
Describe the atomic radius in Group 2
Increases down the group - more electron shells added
Describe the trend in ionisation energy in Group 2
- decreases down the group
- increase in atomic radius and shielding
- easer to remove due to weaker attraction
Describe the trend in electronegativity in Group 2
- decreases down the group
- metal atoms get bigger
- bonding pair further away from nucleus
Describe the trend of melting points in Group 2
- decreases down the group
- outer electrons further from nucleus = shielding
- electrostatic attraction with delocalised electrons and +ions
- less energy to overcome attraction
Describe the visual observations of Grp 2 and water reacting
Be - no reaction Mg - vigorous w/ steam Ca - reacts moderately + Hydroxide Sr - rapidly, Hydroxide Ba - Vigorously + Hydroxide
What is the general equation for Grp2 reactions with water?
M (s) + 2H2O (l) → M(OH)2 (s) + H2 (g)
What is the formula of Mg reacting with steam?
Mg (s) + H2O (g) → MgO (s) + H2 (g)
Describe the trend of reactivity in Grp 2
easier to remove outer electron
Describe the solubility of hydroxides in Grp 2
- Increases as you go down the group
PH increases
Describe the solubility of sulphates in Grp 2
- Decreases down the group
What is Mg(OH)2 in terms of solubitly?
Sparingly soluble
What is the use of Ca(OH)2?
Agriculture
- Slakked lime that works to neutralise acidic soil
How is Mg(OH)2 used in medicine ?
- can be used as antiacids
- indigestion tablets (swallow due to insolubility)
How can BaSO4 be used in medicine?
- Absorbs X-ray (radiocontrast)
- known as “Barium Meal”
- safe as it is insoluble so not absorbed by the body
What is the test for sulphate ions?
- Add HCL
- Then add BaCl2
- Positive result = white p.p of Barium Sulphate
Why do we add HCL in the test for sulphate ions?
Removes unwanted ions (carbonate or sulfate) being made - cause they can give a white p.p
What is the general equation for Group 2 reacting with H2SO4?
M(s) + H2SO4(aq) —-> MSO4(aq) + H2
What is the is general equation with Group 2 with HCL?
M + HCL(aq) —-> MCL2(aq) + H2
What is the general reaction of grp 2 with Oxygen?
2M+O2 —–> 2MO
Describe the observations when Grp 2 react with H2SO4?
Be - Vigorously Mg - Vigorously Ca - Slowed down by sulphate layer Sr - Quickly stopped insoluble layer Ba - Quickly stopped insoluble layer
How is Mg used in the extraction of titanium?
- Mg reduced in 100C
- TiCl4(g) + 2Mg(l) —–> Ti(s) + 2MgCl2(l)
How are CaO (lime) + CaCO3 (limestone) to remove SO2 from flue gas?
- Slurry made by mixing with either and H2O
- Then sprayed on flue gases
- SO2 reacts with alkaline surry
- produces Solid waste = CALCIUM SULFIDE
