Module 2: Group 2 (Alkaline Earth Metals) Flashcards
What is the trend in atomic radius down group 2 & why?
- Increases
- Atomic number increases & shielding increases.
- Extra electron shells are added increasing distance between nucleus & outer electrons.
What is the trend in first ionisation energy down group 2 & why?
- Decreases
- Each element has an extra electron shell compared to the one above (greater atomic radius).
- Electrons lost more easily due to increased shielding.
- Electrostatic attraction between nucleus & outer electrons decreases.
- The increasing positive charge of nucleus (due to extra protons) is overridden by the effect of the extra shells.
What is the trend in reactivity down group 2 & why?
- Increases
- React to lose electrons & form positive ions.
- Energy needed to form positive ions falls due to decrease in ionisation energy.
- Leads to lower Ea & faster reactions.
What is the trend in melting point down group 2 & why?
- Decreases
- Greater shielding & atomic radius offsetting greater nuclear charge.
- Metal ions increase in size so less energy required to break metallic bonds.
- Weaker electrostatic forces of attraction between positive ions & delocalised electrons.
- Drop with Mg as sudden change in crystal structure.
What is the type of bonding found between group 2 atoms?
Metallic bonding
What is the trend in reactivity of group 2 metals with water?
- Increase.
- React with increasing vigour.
- Ionisation energy decreases.
What is produced when group 2 metals react with water?
Metal hydroxide & hydrogen
What is the general reaction for a group 2 metal with water?
M (s) + 2H2O (l) –> M(OH)2 (aq) + H2 (g)
What is the reaction of Mg with cold water?
Mg (s) + 2H2O (l) –> Mg(OH)2 (aq) + H2 (g)
How does Mg react with cold water?
Very slowly
How does Mg react with steam
Rapidly
What is the reaction of Mg with steam?
Mg (s) + H2O (g) –> MgO (s) + H2 (g)
What is the reaction of MgO with cold water?
MgO (s) + H2O (l) –> Mg(OH)2 (aq)
What is the reaction of Ca with cold water?
Ca (s) + H2O (l) –> Ca(OH)2 (aq) + H2 (g)
What is the reaction of Mg with dilute HCl?
Mg (s) + HCl (aq) –> MgCl2 (aq) + H2 (g)
What is the reaction of Ca with dilute H2SO4?
Ca (s) + H2SO4 (aq) –> CaSO4 (s) + H2O (l)
What is observed when Mg is reacted with dilute HCl?
- Exothermic reaction
- Vigorous bubbling
- Effervescence
- Warm test tube
- White precipitate
What is observed when Mg is reacted with dilute H2SO4?
- Exothermic reaction
- Hydrogen gas given off
What is observed when Ca is reacted with dilute HCl?
- Exothermic reaction
- Effervescence
- Warm test tube
- Vigorous reaction
What is observed when Ca is reacted with dilute H2SO4?
- Exothermic reaction
- White precipitate
- Limited reaction
Why is their a limited reaction when Ca reacts with H2SO4 compared to Mg?
CaSO4 is less soluble compared to MgSO4.
What is the trend in solubility of hydroxides?
Solubility increases down the group.
What is the least soluble hydroxide?
Mg(OH)2
What is the most soluble hydroxide?
Ba(OH)2
What is the trend in solubility of sulfates?
Solubility decreases down the group.
What is the solubility of Mg(OH)2 in water?
Sparingly soluble
What is the solubility of BaSO4 in water?
Insoluble in water
What is the use of BaSo4?
- Used in medicine as barium meals.
- Aid in diagnosing problems with oesophagus, stomach or intestines.
- Insoluble, so can’t be absorbed into the bloodstream.
What is the test for sulfate ions?
- Add dilute HCl.
- Add solution of BaCl2
- If sulfate is present, white precipate is produced.
- Ba2+ (aq) + SO4^2- (aq) –> BaSO4 (s)
Why is dilute HCl added when testing for sulfates?
To remove any carbonate ions present that may disrupt results & form a white precipitate of BaCO3.
What is the process of using Mg to extract Ti from its ore?
- Titanium (IV) oxide (TiO2) is converted to titanium (IV) chloride (TiCl4) by heating it with carbon in a stream of chlorine gas.
- TiCl4 is then purified by fractional distillation.
- Then reduced by magnesium in a furnace at
What are the equations for the extraction of Ti using Mg?
- TiO2 (s) + 2Cl2 (g) + 2C (s) –> TiCl4 (g) + 2CO (g)
- TiCl4 (g) + 2Mg (l) –> Ti (s) + 2MgCl2 (l)
What are the conditions for titanium extraction & why?
- Reaction heated under high temperature & inert conditions.
- Mg may react with air & produce inaccurate results
Why is titanium more expensive to produce?
- Titanium requires a series of reactions to extract it from its ore.
- Made in batches which is time consuming & expensive.
What are the properties & use of Mg(OH)2?
- Sparingly soluble.
- Sold as ‘Milk of Magnesia’ in water solution.
- Used in indigestion tablets as an antacid to neutralise excess stomach acid.
What are the properties & use of Ca(OH)2?
- Sparingly soluble.
- Solution used as lime-water.
- Used in agriculture to neutralise acidic soils.
What is wet scrubbing?
The process of removing acidic sulfur dioxide from flue gases by reacting them with an alkali.
Name two alkalis that can be used in wet scrubbing?
- Calcium oxide (Lime, CaO).
- Calcium carbonate (Limestone, CaCO3).
What is the process of removing SO2 from flue gases (west scrubbing)?
- A slurry is made by mixing CaO or CaCO3 with water.
- This is sprayed onto the flue gases.
- SO2 reacts with the alkaline slurry to produce a solid, waste product of CaSO3.
What are the equations for the removal of SO2 from flue gases (wet scrubbing)?
- CaO (s) + 2H2O (l) + SO2 (g) –> CaSO3 (s) + 2H2O (l).
- CaCO3 (s) + 2H2O (l) + SO2 (g) –> CaSO3 (s) + 2H2O (l) + CO2 (g).
