4- Inorganic chemistry and the periodic table Flashcards
Define thermal decomposition.
A reaction in which a compound breaks down under heating,
Group 1 metals are powerful ______ _______?
Reducing agents.
For group one, what is the trend in reactivity down the group?
Increases.
Give 3 reasons why sodium and potassium are used regularly as chemical reagents?
- Ions of Group one metals are fairly unreactive so act as spectator ions.
- Most of their compounds are soluble in water, including hydroxides and carbonates.
- Ions are colourless in aq sol. so don’t interfere with or hide colour changes.
Explain steps for a flame test of group one metals.
Dip nichrome wire in concentrated HCl, as chlorides evaporate easier so flames are coloured more strongly. Then, dip wire in sample crystals. Finally, place wire in Bunsen flame,
What colour are Lithium ions in a flame test?
Bright red.
What colour are Sodium ions in a flame test?
Bright yellow.
What colour are Potassium ions in a flame test?
Lilac.
Group two compounds are _________ in water.
Insoluble.
Group 2 metals are _______ _______ ?
reducing agents
Describe the reaction of group 2 elements with oxygen.
Form white ionic oxides of M2+ and O2-.
What colour flame does Magnesium cause when burnt in oxygen?
White.
What colour flame does Calcium cause when burnt in oxygen?
Red.
What colour flame does Barium cause when burnt in oxygen?
Green.
Compound formed when Barium is burnt in oxygen?
Barium peroxide.
BaO2.
Explain the reaction of Magnesium with water.
Magnesium reacts slowly in cold water producing Mg(OH)2
Reacts much quicker heated in steam and produces MgO and H2 gas.
Reaction of Calcium and cold water?
Ca(OH)2 and H2 gas.
Barium with water?
Reacts quickly and it hydroxide is more soluble.
Group two reaction with chlorine?
On heating:
M(s) + Cl2 (g) –> MCl2 (s)
Solubility of group two oxides? (M(OH)2)
Increases down the group
What does calcium hydroxide form when dissolved in water?
Limewater.
Equation for limewater test for carbon dioxide?
Ca(OH)2 + CO2 -> CaCO3 +H2O
General trend for solubility of G2 compounds?
If both ions are small or both ions are big, they tend to be insoluble.
Which group 2 hydroxide is most soluble?
Barium hydroxide
Barium carbonate is ________ in water?
insoluble
Properties of group 2 carbonates?
Insoluble in water, react with dilute acids, decompose on heating.
General equation for decomposition of G2 carbonates on heating?
MCO3 -> MO(s) + CO2(g)
Trend in ease of decomposing?
Harder to decompose down the group. More thermally stable.
Properties of G2 Nitrates?
All have formula M(NO3)2. Colourless crystalline solids , very soluble in water. Decompose to form oxide when heating (MO).
They become more difficult do decompose down the group.
Equation for decomposing of G2 nitrates?
2M(NO3)2 (s) ->2MO (s) + 4NO2 (g) + O2(g)
Properties of G2 sulfates?
All colourless solids with formula MSO4.
Become less soluble down the group.
Test for sulfate ions?
Add barium chloride or barium nitrate (Ba2+) to acidified solution. White precipitate should form.
Ba2+ + SO4 2- -> BaSO4 (s)
Flame colour of Beryllium and Magnesium?
No colour
Flame colour of Calcium?
Brick red
Flame colour of Strontium?
Bright red
Flame colour of Barium?
Pale green
Trend in thermal stability for G1 and G2 nitrates and compounds? Explain
More stable down the group. This is because the larger positive ions have a lower charge density, and therefore distorts the carbonate/ nitrate ion less, making it more stable. G2 less stable generally than G1.
G7 London forces trend and why. Melting temp?
Increase down group as more electrons. MP rises down group.
Chlorine oxidation state and exceptions?
Normally -1 but can be positive if oxidised by oxygen and fluorine.
Halogens solubility?
More soluble in organic solvents than water.
What determines if phosphorous and chlorine make PCl3 or Pcl5?
Whether Chlorine gas is in excess or not.
Determining which halide?
AgNO3 added to solution of halide ions.
Chloride turns white
Bromide turns Cream
iodide turns Yellow.
Reaction of NaCl in conc. H2SO4?
HCl fumes form, NaHSO4 remains. Cl is the weakest reducing agent (strongest [O] most likely to form negative ions) .No redox, just acid base.
Reaction of NaBr in conc. H2SO4?
Br2 vapour (orange) and SO2 gas form (colourless). Some HBr forms, Solid NaHSO4 formed. Redox reaction, Br has some reducing power (is oxidised itself to Br2 from Br-). Sulfur is reduced from +6 to +4. Also acid base (HBr formed).
Reaction of NaI in conc. H2SO4?
Dark solid of I2 forms which gives off purple vapour when heated. Some Sulfur is formed and H2S is formed. Redox reaction, Iodine reduces Sulfur to 0 in S and 2- in H2S.
Hydrogen halides properties?
Colourless gas at room temp.
Very soluble in water, ionise completely. Strong acids.
HX with NH3?
White smoke of ammonium salt. NH4 (+)X(-) (s).
Cl2 and Br2 reaction with water?
H20 + X2 -> HXO (aq) + Hx(aq)
Disproportionation. Reversible. Greater reaction with Cl than Br.
Iodine insoluble in water, barely reacts.
Reaction of Cl2 in Sodium or potassium hydroxide?
Cl2 + 2OH- -> ClO- + Cl- + H2O(l)
Heating of Chlorate (I) ions?
Disproportionation.
3ClO- -> ClO3- + 2Cl-
Overall equation for reaction of Chlorine with hot potassium hydroxide?
How do bromine and iodine react?
3Cl2 + 6OH- -> ClO3- +5Cl- +3H20
Similarly, but their XO- ions are less stable so disproportionate at a lower temp.
