Group 2 & 7 and Qualitative Analysis
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What is the most reactive metal in group 2 ?
Barium
The highest energy electrons of group 2 metals are in which subshell ?
S subshell
Does reactivity increase or decrease down group 2 ?
Increases as electrons are lost more easily because larger atomic radius and more shielding
What happens to the first ionisation energy as you go down group 2 ?
*it decreases because *increased electron shielding *increased atomic radius *less energy needed to remove electron
What type of reaction is between group 2 elements and oxygen or water vs group 2 compounds
*group 2 elements- redox reaction *group 2 compounds- neutralisation reaction
Which group 2 element doesn’t react with water and which one reacts very slowly in water ?
Beryllium (doesn’t react with water) Magnesium (reacts very slowly)
What is oxidised and what is reduced in a reaction between group 2 metal and water ?
*metal - oxidised *one hydrogen from each water- reduced
What is the formula for group 2 with acids ?
Metal + acid -> salt + hydrogen gas
What is formed when group 2 oxides react with water and an example ?
Metal hydroxide Eg MO(s) + H2O(l) ——->M(OH)2 (aq)
Which group 2 metal is insoluble in water ?
Beryllium oxide
What is the trend in hydroxide solubility down group 2 ?
Increases down the groups Mg(OH)2 is slightly soluble Ba(OH)2 creates a string alkaline solution
What is Ca(OH)2 used for and write its hydroxide equations?
Used to neutralise soil Ca(OH)2 (aq) + 2HCL (aq) —-> 2H2O (l) + CaCl2 (aq)
What is Mg (OH)2 used for ?
Milk of magnesia - antacid to treat indigestion (heartburn)
Calcium carbonate use?
*Present in limestone ans marble *used in building construction
What is the drawback of using calcium carbonate in construction and write the equation?
Group 2 carbonates react with acid CaCO3 (s) + 2HCl (aq) —-> CaCl2 (aq) + H2O (l) + CO2(g)
What is the trend if boiling points down group 7 ?
Increases down the group because the size of the atom increases as more occupied electrons shells and stringer London forces attraction between molecules
Trend of reactivity down group 7?
Reactivity decreases *atomic radius increases *electron shielding increases *ability to gain an electron and form 1- ions decreases
What is it called when a more reactive halogen displaces a less reactive halide ?
Displacement reaction
What is the colour or chlorine ,bromine and iodine in water ?
Chlorine - pale green Bromine -orange Iodine - brown
What is the colour of Chlorine ,bromine and iodine in alkane ?
Chlorine - pale green Bromine - orange Iodine - violet
Bromine and iodine can be oxidised by chlorine. Write the equation for chlorine oxidising both bromide and iodide ions ?
Bromide - CL2 (aq) + 2Br-(aq) ——>2Cl- (aq) + Br2 (aq) Iodide - CL2 (aq) + 2I- (aq) ——> 2Cl-(aq) +I2 (aq)
Which halide can iodine oxidise ?
Iodine does not oxidise Cl- or Br-
Define disproportionation ?
The oxidation and reduction of the same element in a redox reaction
The reaction between chlorine and water is disproportionation reaction and what is the equation for CL2 with water ?
Cl2 (g) + H2O (l) ——> HClO (aq) + HCl (aq )