Section 2 - Group 2 and Group 7 Elements Flashcards
What type of ions do group 2 metals form?
2+ ions.
What is the trend in atomic radius down group 2 and why?
Increases - extra electron shells are added.
What is the trend in First Ionisation Energy down group 2 and why?
Decreases because…
- electron shells increase
- shielding occurs
- electrons are futher from nucleus
What is the trend in reactivity down group 2 and why?
Increases because…
- First IE decreases
- Easier to lose electrons
What is the trend in mpts down group 2 and why?
Decreases…
- they have metallic structures
- metal ions get bigger but no. of electrons stays the same
- larger ionic radius means the electrons are further from the nuclei
What are group 2 elements reduced or oxidised when reacted?
Oxidised
What is the trend in solubility when reacting Mg, Ca, Sr and Ba with OH-?
Increases
What is the trend in solubility when reacting Mg, Ca, Sr and Ba with SO42-?
Decreases.
What is the solubility of Mg(OH)2?
Sparingly soluble
What is the solubility of BaSO4?
Insoluble
What is the test for sulfate ions?
Add acidified barium chloride to a solution containing sulfate ions and a white precipitate of barium sulfate will form.
Why must you acididfy the solution in the sulfate ions test?
To get rid of lurking sulfites or carbonates which would also produce a white precipitate
What can be used to neutralise acid soils?
Calcium hydroxide (Ca(OH)2)
What can be used to neutralise excess stomach acid?
Magnesium hydroxide (Mg(OH)2)
Give the ionic equation for neutralisation:
H+(aq) + OH-(aq) —> H2O(l)
Explain the barium meal:
- a patient swallows a suspension of barium sulfate
- it coats their tissues
- it is opaque to x-rays so the tissues are visible
Explain how magnesium can be used to extract titanium from its ore and give the equation:
TiCl4(g) + Mg2(g) —> Ti(s) + 2MgCl(l)
- TiO2 (the main titanium ore) is converted to titanium chloride (TiCl4) by heating it with carbom in a stream of chlorine gas
- the titanium chloride is then purified by fractional distillation
- it is reduced by Mg in a furnace at almost 1000oC
Explain how calcium oxide and calcium carbonate can be used to remove sulfur dioxide and give the equations:
CaO(s) + 2H2O(l) + SO2(g) —> CaSO3(s) + 2H2O(l)
CaCO3(s) + 2H2O(l) + SO2(g) > CaCO3(s) + 2H2O(l) + CO2(g)
- powdered calcium oxide (CaO) and calcium carbonate (CaCO3)
- a slurry is made by mixing these with water
- it’s sprayed onto the flue gases
- a solid waste product of calcium sulfite is formed
What is the trend in electronegativity down group 7?
Decreases…
- electrons are further from the nucleus
- outer electrons are shielded by inner electrons
What is the trend in bpts down group 7?
Increases…
- relative mass increases
- strength of Van der Waals increases
What colour is F2?
Pale yellow
What state is F2?
Gas
What colour is Cl2?
Green
What state is Cl2?
Gas
What colour is Br2?
Red-brown
What state is Br2?
Liquid
What colour is I2?
Grey
What state is I2?
Solid
What is the trend in reactivity down group 7 and why?
Decreases…
- atoms become larger
- distance between electrons and nucleus increases
A halogen will displace a halide ion from solution if the halide is _____ it in the periodic table.
Below
What is the trend in oxidising strength down group 7?
Decreases
Which ions will chlorine displace?
Br- and I-
Which ions will bromine displace?
I-
Which ions will iodine displace?
None
What can be observed in a reaction between colourless chlorine water and colourless KCl solution?
No reaction
What can be observed in a reaction between colourless chlorine water and colourless KBr solution?
Orange solution of Br2 formed
What can be observed in a reaction between colourless chlorine water and colourless KI solution?
Brown solution of I2 formed
What can be observed in a reaction between orange bromine water and colourless KCl solution?
No reaction
What can be observed in a reaction between orange bromine water and colourless KBr solution?
No reaction
What can be observed in a reaction between orange bromine water and colourless KI solution?
Brown solution of I2 formed
What can be observed in a reaction between brown Iodine water and colourless KCl solution?
No reaction
What can be observed in a reaction between brown Iodine water and colourless KBr solution?
No reaction
What can be observed in a reaction between brown Iodine water and colourless KI solution?
No reaction
What do chlorine and sodium hydroxide make?
Bleach
Give the equation to make bleach:
2NaOH(aq) + Cl2 —> NaClO(aq) + NaCl(aq) + H2O(l)
Is chlorine oxidised or reduced in the reaction to make bleach?
Both! This is called disproportionation
What is it called when an element is both oxidised and reduced in a reaction?
Disproportionation
Give 4 uses of bleach:
- Water treatment
- Bleaching paper
- Bleaching textiles
- Cleaning toilets
Does chlorine get oxidised or reduced when it reacts with water?
Both - disproportionation
Give the equation for the formation of chloride ions and chlorate ions from chlorine and water:
Cl2(g) + H2O(l) ⇌ 2H+ + Cl-(aq) + ClO-(aq)
Give the equation for the decomposition of water in sunlight form chloride ions and oxygen:
2Cl2(g) + 2H2O(l) ⇌ 4H+ + 4Cl- + O2(g)
Give 3 positives for the treatment of water with chlorine:
- Kills disease-causing microorganisms
- Some chlorine stays in water and prevents reinfection
- Prevents growth of algae (and therefore bad tastes, smells and discolouration)
Give 2 negatives for the treatment of water with chlorine:
- Chlorine gas is harmful if inhaled
- Liquid chlorine causes chemical burns
- Could form chlorinated hydrocarbons which can cause cancer (but consider the health effects of unsafe drinking water)
What is the trend in reducing power down group 7?
Increases…
- Ions get bigger - electrons further from nucleus
- more shielding
Give the equation for the reaction of NaF with H2SO4?
NaF(s) + H2SO4(aq) —> NaHSO4(s) + HF(g)
Give the equation for the reaction of NaCl with H2SO4?
NaCl(s) + H2SO4(aq) —> NaHSO4(s) + HCl(g)
