Chapter 8 Flashcards
What is the other name for a G2 element?
A reducing agent as it reduces another species.
What happens when a G2 metal reacts with oxygen, water or a dilute acid?
Oxygen = a metal oxide (XO). Water = alkaline hydroxide (M(OH)2) and H2. Acid = salt and hydrogen.
What is the reactivity trend for G2?
Increases down group so become stronger reducing agents. More inner shell shielding, increased radius, decreased nuclear attraction.
What happens when G2 oxides react with water?
Release OH- ions to form alkaline solutions of the metal hydroxide.
What happens when G2 hydroxides react with water?
They are slightly soluble but in excess the solution becomes saturated and the rest forms a white precipitate.
What happens to the solubility/pH of G2 hydroxides down G2?
Solubility of hydroxides increase so pH increases (alkalinity increases) down the group.
What are the uses of G2 compounds?
Agriculture: added to fields to inc. pH of acidic soils by neutralisation.
Medicine: G2 bases as antacids for treating acid indigestion e.g milk of magnesia.
What is the other name for a G7 non-metal?
Oxidising agents as in a reaction the other species will be oxidised.
What happens to melting/boiling points down G7?
Increases as London forces increase (diatomic molecules at RTP) as there are more electrons. Takes more energy to overcome these.
What are the colours of the G7 non metals in water and non-polar solvents?
Chlorine is pale green, bromine is orange and iodine is brown. In non-polar solvents the colour is more intense and iodine is violet (as the halogens dissolve more readily than in water).
What happens in a displacement reaction?
The more reactive halogen displaces a halide ion. The solution turns the colour of the old ion (and the colour of the new halogen product formed)
What is the reactivity trend of G7?
Reactivity decreases down group as G7’s need to gain electrons by attracting another. Atomic radius increases, more inner shell shielding, less nuclear attraction to gain/attract an electron. Oxidising ability decreases down group.
What is a disproportionation reaction?
It is a redox reaction in which the same element is both oxidised and reduced. Happens typically when G7 elements react with water and alkalis
What are the tests for halide ions?
Add silver nitrate to sample. Cl = white precipitate, soluble in dilute NH3. Bromine = cream precipitate, soluble in concentrated NH3. Iodine = yellow precipitate, insoluble in concentrated NH3.
What is the test for carbonate ions?
Add dilute nitric acid to sample. Forms CO2 which when bubbled through limewater turns cloudy. Observation - effervescence.
