10. Group 2 Flashcards
Reaction of Mg with oxygen
- burns in oxygen on heating with a white flame
- white MgO solid formed
Reaction of Ca with oxygen
- burns in oxygen on heating with a brick-red flame
- white CaO solid formed
Reaction of Sr with oxygen
- burns in oxygen on heating with a red flame
- white SrO solid formed
Reaction of Ba with oxygen
- burns in oxygen on heating with a green flame
- white BaO solid formed
Reaction of Mg with water
- reacts very slowly with cold water to form a white precipitate of Mg(OH)2
- effervescence due to hydrogen gas - reacts vigorously with steam and burns with a white flame to form white MgO solid
- effervescence due to hydrogen gas
Reaction of Ca with water
- forms a cloudy white suspension of slightly soluble Ca(OH)2 / water turns milky
- bubbles produced
- calcium sinks
- calcium gets smaller / disappears
Reaction of Sr with water
- faster bubbling
- faster disappearance of Sr
- no precipitate is formed in excess water
Reaction of Ba with water
- even faster bubbling
- even faster disappearance of Ba
- no precipitate is formed in excess water
Reaction of Group 2 elements with dilute hydrochloric acid / dilute nitric acid
- all react with dilute HCl/HNO3 to give bubbles of hydrogen and a colourless solution of the metal chloride / metal nitrate
- reaction becomes more vigorous down the group
Reaction of Mg with dilute sulfuric acid
- bubbles of hydrogen gas produced
- colourless solution of MgSO4 formed
Reaction of Ca with dilute sulfuric acid
- some bubbles of hydrogen gas produced
- white precipitate of CaSO4 formed, which is sparingly soluble
Reaction of Sr with dilute sulfuric acid
- very slight bubbles of hydrogen gas produced
- white precipitate of SrSO4 formed, which is insoluble
Reaction of Ba with dilute sulfuric acid
- very slight bubbles of hydrogen gas produced
- white precipitate of BaSO4 formed, which is insoluble
Reaction of MgO with water
- sparingly soluble / insoluble in water to form a white precipitate of Mg(OH)2 and a weakly alkaline solution, pH=9
Reaction of CaO with water
- slightly soluble in water to form milky solution and an alkaline solution, pH=11
Reaction of SrO with water
- soluble in water to form a colourless alkaline solution, pH=12
Reaction of BaO with water
- soluble in water to form a colourless alkaline solution, pH=13
Reaction of Group 2 oxides with dilute hydrochloric acid / dilute nitric acid
- all react with dilute HCl/HNO3 to give a colourless solution of the metal chloride / metal nitrate (and water)
Reaction of MgO with dilute sulfuric acid
- reacts to form a colourless solution of MgSO4
Reaction of CaO with dilute sulfuric acid
- reacts to form a white precipitate of CaSO4, which is sparingly soluble
Reaction of SrO with dilute sulfuric acid
- reacts to form a white precipitate of SrSO4, which is insoluble
Reaction of BaO with dilute sulfuric acid
- reacts to form a white precipitate of BaO, which is insoluble
Behaviour of Group 2 hydroxides with water
Variation in solubility of the hydroxides
- do not react with water
- none of them are very soluble, but the solubility of the metal hydroxides increases down the group
- alkalinity increases / stronger base down the group
Reaction of Group 2 hydroxides with dilute acids
- the hydroxides behave exactly like the oxides, forming salt and water (both oxides and hydroxides are basic)
Behaviour of Group 2 carbonates with water
- do not react with water
- all are insoluble in water
Reaction of Group 2 carbonates with dilute hydrochloric acid / dilute nitric acid
- all react with dilute HCl/HNO3 to give bubbles of carbon dioxide gas and a colourless solution of metal chloride / metal nitrate (and water)
Reaction of Group 2 carbonates with dilute sulfuric acid
Variation in solubility of the carbonates
- bubbles of CO2 gas produced
- solubility of the metal carbonates decreases down the group
- only MgSO4 is soluble, giving a colourless solution
- the others form insoluble, white precipitates
Thermal decomposition of Group 2 carbonates
- decompose on heating to leave a metal oxide residue and CO2 gas (forms a white precipitate with limewater)
- decomposition temperature / thermal stability increases down the group; ease of thermal decomposition decreases down the group
Thermal decomposition of Group 2 nitrates
- decompose on heating to leave a metal oxide residue, brown NO2 gas and O2 gas (relights glowing splint)
- decomposition temperature / thermal stability increases down the group; ease of thermal decomposition decreases down the group
Use of calcium hydroxide and calcium carbonate (powdered limestone) in agriculture
- CaCO3 decomposes to form CaO (lime/quicklime)
- CaO reacts with water in a hydration reaction to form Ca(OH)2 (slaked lime)
- calcium hydroxide and calcium carbonate are used to reduce acidity in soil/increase pH of soil, as they are basic
- but CaCO3 is more suitable b/c it is insoluble in water, so it is less likely to be washed away by rain
Explain why there is no visible reaction when a piece of magnesium ribbon is exposed to the air. [2m]
- activation energy is high
- so few/no particles with E >= Ea
