Chapter 8 Flashcards
Reactivity trend down group 2?
Increases down group
Why does the reactivity of group 2 increase down group?
The ionisation energy decreases down the group because the attraction between nucleus and valence electrons decrease as a result of increasing atomic radius and shielding. This makes it easier to remove an electron down the group
Solubility of hydroxides in group 2?
Increases down rhe group resulting in more OH- ions and are more alkaline
Trends of hydroxides in group 2?
pH increases
Alkalinity increases
Solubility increases
Uses of group 2 compounds in agriculture?
Ca(OH)2 is used to increase pH of acidic soils
It neutralises acid to form neutral water
Treating acid digestion
Mg(OH)2 and CaCO3 are used in indigestion tablets
Trends down halogen group?
More electrons
Stronger London forces
More energy required to break IMF
Boiling point increases
Reactivity decreases
Atomic radius increases
Shielding increases
nuclear attraction decreases
What is disproportionation?
Redox reaction which same element is both oxidised and reduced.
Example is chlorine with water and with cold dilute sodium hydroxide
Benefits and risks of chlorine
Kills bacteria in water and ensures water can be drinkable
Chlorine is a respiratory irritant in small concentrations and large concentrations can be fatal
It can react with organic hydrocarbons like methane. This forms chlorinated hydrocarbons which are suspected of causing cancer
However the benefits outweigh the risks as it prevents cholera and typhoid outbreaks
Test for halide ions
Aqueous halide ion + aqueous silver ion —> precipitate of silver halide
1) add AgNO3 to aqueous solution of halide
2) silver halide precipitates have different colours - chloride is white, bromide is cream and iodide is yellow
3) add aqueous ammonia to test solubility of precipitate as it is hard to differentiate the colours of the three halide precipitates
2Cl- + Br2 —>
No reaction
2Cl- + I2 —>
No reaction
2Br- + Cl2 —>
Orange colour from Br2 formation
Cl2 + 2Br- —> 2Cl- + Br2
2Br- + I2 —>
No reaction
2I- + Cl2 —>
Violet colour from I2 formation
Cl2 + 2I- —> 2Cl- + I2
2I- + Br2 —>
Violet colour from I2 formation
Br2 + 2I- —> 2Br- + I2