Topic 4 - Inorganic Chem & Periodic Table Flashcards
Inorganic Chemistry and the periodic table
Why does ionisation energy decrease down G2 ? (reactivity increases)
- extra electron shell (shielding)
- outer electrons further away from the nucleus (lower electrostatic attraction)
What are the solubility trends depending on the compound anion?
- Group 2 elements that contain single charged negative ions INCREASE in solubility down the group
- Compounds that contain double charged negative ions DECREASE in solubility down the group
What happens when G2 burns in oxygen ?
produces metal oxides (solid white)
What is the solubility trends as you go down Group 2 when you react with hydroxide?
Increases down the group
What happens when G2 reacts with chlorine ?
produces metal chlorides (solid white)
Which G2 does not produce an alkaline when added to water ?
- beryllium (oxide) - doesn’t react with water
beryllium (hydroxide) - insoluble - magnesium (oxide) - reacts slowly
magnesium (hydroxide) - low solubility
What is the solubility trends as you go down Group 2 when you react with sulfate?
Decreases down the group
What sulfate is insoluble in water?
Barium sulfate
What are compounds like magnesium hydroxide known to be ?
sparingly soluble because they have a low solubilty
EQUATION when metal oxides react with water
MO(s) + H2O(l) -> M(OH)2(aq)
EQUATION when metal hydroxides react with water
M(OH)2(s) –+H2O(l)–>M(OH)2(aq)
EQUATION when metal hydroxides react with dilute acid
M(OH)2(aq) + 2HCl(aq) –> MCl2 (aq) +2H2O(l)
EQUATION when metal oxides react with dilute acid
MO(s) +2HCl(aq) –> MCl2(aq) + H2O(l)
What is the flame colour of Li?
Red
Trend of thermal stability in G1 and G2 ?
increases down a group
What is the flame colour of Na?
orange/yellow
What is the flame colour of K?
lilac
What is the flame colour of Rb?
red
What is the flame colour of Cs?
blue
How are G1/G2 carbonate and nitrate ions made unstable ?
they are large anions made unstable by the presence of a cation as it polarises the anion (distorting it) - greater distortion = less stable
What is the flame colour of Ca?
brick-red
What is the flame colour of Sr?
crimson
What is the flame colour of Ba?
green
How do you do a flame test in 3 steps:
- MIX a small amount of the compound you’re testing with a few drops of hydrochloric acid.
2.HEAT a piece of platinum or nichrome wire in a hot Bunsen flame to clean it
3.DIP the wire into the compound/acid mixture. Hold it in a very hot flame and note the colour produced.
What causes most distortion ?
smaller cations - higher charge density
Why do bunsen burners produce different colours depending on the compound used?
Energy absorbed from flame= electrons move to higher energy levels.
Colours seen as the electrons fall back down to lower energy levels=release energy in the form light.
Difference in energy as electron move from higher and lower levels determines the wavelength of the light released= makes the colour of the light.
EXPLAIN the trend in thermal stability of G1/G2 ?
further down the group = larger cation = lower charge density = less distortion = more stable carbonate/nitrate ion
Which compounds are more thermally stable ? (G1 or G2)
Group 1
Why are G2 compunds less thermally stable than G1 compunds ?
- the greater the charge on cation, the greater the distortion and less stability
- G2 have +2 charge compared to a +1 charge
- therefore less stable
How to test the thermal stability of nitrates.
- measure how long it takes until a certain amount of oxygen is produced
- measure how long until an amount of brown gas is produced
How to test the thermal stability of carbonates
- how long it takes for an amount of CO2 to be produced
CO2 test- add limewater which is a saturated solution of calcium hydroxide.Turns cloudy
Do Group 1 carbonates decompose? and if they do which one can decompose.
they are thermally stable - you can’t heat them w a bunsen burner to make them decompose
HOWEVER THERE IS ALWAYS ONE SPECIAL ONE, Li2CO3 which decomposes to Li2O and CO2
Do Group 2 carbonates decompose?
they do decompose and they form an oxide and carbon dioxide
General formula: MCO3 –> MO + CO2
E.g. CaCO3 –> CaO + CO2
Do G2 nitrates decompose ?
yes - forms metal oxide, nitrogen dioxide and oxygen
general formula : 2M(NO3)2
—-> 2MO + 4NO2 + O2
What is the colour of fluorine?
pale yellow
What type of reaction is a halogen and halide reaction?
redox (displacement)