inorganic chem 4

What happens to the atomic radius of group 2 metals

Increases down due to additional electron shells

What happens to the reactivity of group 2 metals

increases down the group as increased electron shielding and increased atomic radius down the group makes the outer electrons easier to lose

What happens to the ionisation energy of group 2 metals

Decreases down the group due to greater atomic radius and increased shielding. This makes the electrons easier to remove.

How does group 2 react with water. Plus what would happen with steam (Mg example)

Reacts in redox reactions to produce a metal hydroxide and hydrogen. e.g. Mg + 2H2O → Hg(OH)2 +H2.

The reaction is faster with steam as it provides the reaction extra energy.

Mg burns in stream with a bright white flame to form H2 and MgO (a white powder)

Group 2 reactions with Chlorine

Reacts with Cl2 gas to form metal chlorides.

They’re all white precipitates.

The reaction becomes more vigorous as you move down as the elements are more reactive

Group 2 reactions with oxygen

Reacts with oxygen to form oxides (MO).

Once the reaction has been initiated it’s vigorous.

Strontium and barium can react with excess oxygen and heat to form metal peroxides (MO2)

Group 2 reactions with dilute acids

Reacts to produce bubbles of H2 gas and solutions of metal compounds.

Group 2 hydroxides reacting with dilute acid

Reacts to form a salt and water. It’s a type of neutralisation reaction

Solubility of group 2 hydroxides and as a result, their uses

it increases down the group.

It varies allowing them to have different uses.

Mg(OH)2 is least soluble and is used in medicine as it’s alkaline and can neutralise acids. Also used in this way in agriculture to neutralise acidic soil.

Solubility of group 2 sulfate and as a result, their uses

Decreases down the group.

The insolubility of BaSO4 is used in medicine as barium meals (a form of medical tracer that allows tissues to be imaged. Is toxic if enteres the bloodstream but is insoluble so can’t be absorbed into the blood so is completely safe)

Conditions needed for thermal decomposition of group 2 carbonates and nitrates. And what is produced

produces solid metal oxides and a gas.

Done by heating substance in aerobic conditions (lots of oxygen)

What’s happens in the thermal decomposition of group 2 carbonates

Produce CO2 and metal oxide (white powder).

As you go down group 2, more best is required as the ions increase in size and the carbonates increase in thermal stability

What happens in the thermal decomposition reaction of group 2 nitrates

Produce nitrogen dioxide, oxygen, and metal oxide (white powder).

More heat required as you go down as the ions increase in size and the nitrates increase in thermal stability

Do group 1 metals also undergo thermal decomposition

Group 1 carbonates and nitrates do with heating in aerobic conditions.

How does lithium thermally decompose

Same as group 2 elements.

Lithium nitrate → lithium oxide + nitrogen oxide + oxygen.

Lithium carbonate → lithium oxide + carbon dioxide.

How does the rest of group 1 react in thermal decomposition

They rarely go to completion.

Group 1 nitrates → metal nitrate + oxygen.

Group 1 carbonates → won’t decompose as they require extremely high temperatures to do so

Explanation of the thermal stability trend of group 1 and 2

Elements of group 1 and 2 form more stable carbonates and nitrates as you go down, and so require more heat energy to undergo thermal decomposition.

As you go down, ionic radius increases for the same overall charge. The smaller ions have a higher charge density.

The smaller ions are able to polarise the negative carbonate and nitrate ions more, and the more the negative ion is polarised, the less heat is required to separate the two ions. So smaller ions form less stable carbonates and nitrates.

Flame test procedure

1) put nichrome wire in solution of concentrated HCl then into a blue Bunsen burner flame.

2) repeat until there’s no colour in the flame.

3) dip the wire into the unknown metal compound and place it into the flame

Flame test colours for Li, Na, K, Mg, Ba, Sr, Ba

Li= red, Na= yellow, K= lilac, Mg= colourless, Ca= brick red, Sr= crimson red, Ma= pale green

Explanation of the formation of flame test colours

Electron transitions.

When energy (from Bunsen) is absorbed by the species, some e- will be promoted to orbitals which have higher energy. The e- will drop back down to the og orbital they were in and during this process they release energy, some of which in the form of light.

The colour produced depends on the wavelength of light emitted. Not all atoms produce colour cus for them, when some e- drop back to their og orbital, the energy emitted may not have a wavelength in the visible part of the em spectrum

What happens to the atomic radius of group 7

Increases down the group due to additional electron shells

What happens to the electronegativity of group 7

Decreases as you go down.

because as you go down, atomic radius and electron sheen ding increases. So electrons in th Souter shells are less strongly attracted to the nucleus so are more easily removed.

What happens to melting and boiling point in group 7

Increases as you go gown.

In group 7 they’re simple covalent molecules with London forces. The strength of the intermolecular increases as the Ar of the molecule increases. So the strength of the London forces increases down the group. So more energy is needed to overcome them so higher boiling points.

What happens to the reactivity down group 7

Decreases as the atomic radius increases making it harder to gain e- as the positive attraction of the nucleus is weakened by additional shielding

How are Halogens as oxidising agents

Good oxidising agents as they accept e- from the species being oxidised or reduced.

This oxidising power decreases down the group as their ability to attract e- decreases due to shielding and a greater atomic radius.

What is relative oxidising strength

Means a halogen will displace any halide beneath it in the periodic table.

Cl2 will displace Br- and I-. Br2 will displace I-. I2 will displace none

How are Halide ions as reducing agents

Good reducing agents cus they donate e- to species being reduced and are themselves oxidised.

This reducing power increases down the group as e- are easier to lose from larger ions due to shielding and a larger atomic radius

What does the redox reactions between halides and H2SO4 depend on

Depends on the reducing ability of the halide.

The reducing ability of the halide can be observed by the relative reactions of the halides with sulfuric acid (H2SO4)

What happens in the redox reaction determining the reducing ability of F- and Cl- ions

NaF + H2SO4 → NaHSO4 + HF.

NaCl + H2SO4 → NaHSO4 + HCl.

No further reactions take place since HF and HCl are not string enough reducing agents to reduce H2SO4.

HF and HCl will both be observed as misty fumes

What happens in the redox reaction determining the reducing ability of Br- ions

NaBr + H2SO4→ NaHSO4 + HBr.

2HBr + H2SO4 → Br2 + SO2 + 2H2O.

HBr will be observed with misty fumes from the first reaction. Orange fumes of Br2 and choking fumes of SO2 will be observed in the second reaction where HBr reduces H2SO4

What happens in the redox reaction determining the reducing ability of I- ions

NaL + H2SO4 → NaHSO4 + HI.

2HI + H2SO4 → I2 + SO2 + 2H2O.

6HI + SO2 → H2S + 3I2 + 2H2O.

HI will be observed as misty fumes form the first reaction. HI then reduces H2SO4 to solid iodine and choking fumes of SO2. The HI will then further reduce the SO2 to toxic gas H2S

What happens to reducing power in group 7 and what does it have to do with reactions

Increases down group 7.

The greater the reducing power, the further the reaction will proceed as the halide is powerful enough to reduce more species

What happens when chlorine reacts with cold water

Cl2 + H2O → ClO- + Cl- + 2H+.

It’s a disproportionation reaction as the Cl is both oxidised and reduced.

This reaction is used in water treatment systems to kill bacteria. Cl can be toxic but the benefits of clean water outweigh it

What happens when group 1 and 2 metals react with chlorine gas

Form metal chlorides which are all wits precipitates

what happens when you add acidified silver nitrate to Cl- Br- and I-

AgCl (white ppt).

AgBr (yellow ppt).

AgI (yellow ppt)

What happens to the ppt when you add dilute ammonia to AgCl, AgBr, AgI

Cl- = ppt dissolves.

Br- = no change.

I-= no change

What happens to the ppt after you add concentrated ammonia to AgCl, AgBr, AgI

Cl- = ppt dissolves.

Br- = ppt dissolves.

I- = no change

What happens when you react hydrogen halides (HCl, HBr, HI) with ammonia gas

Forms ammonium salts. The hydrogen halides are strong acids in solution and react with ammonia in an acid-base reaction to form a salt.

E.g. HCl + NH3 → NH4Cl

How to hydrogen halides react with water

Form dilute acids. In solution these strong acids dissociate to release their halide ions and hydrogen ions. The hydrogen ions form a hydroxonium ion with water molecules in a solution. The resulting solution is acidic.

E.g. HCl + H2O → Cl- + H3O+

Anion vs cation

Anion= negative ion.

Cation= positive ion

Test for sulfate (SO4 2-) anion

Add acidified barium chloride which reacts to form a white ppt of barium sulfate.

BaCl2 + XSO4 → BaSO4 (white ppt) + XCl2

Test for carbonate (CO3 2-) and hydrocarbonate (HCO3 -)

Add acid e.g. HCl, the substance containing carbonate ions will fizz and CO2 gas is given off. The gas is collected and bubbled through limewater which will turn cloudy.

XCO3 + 2HCl → CO2 + H2O + XCl2

Test for ammonium (NH4 +)

Add NaOH and gently warming it forms ammonia gas (which is basic). Therefore the presence of ammonium ions can be tested by holding damp litmus paper over a Petri dish of the substance being tested. It’ll turn blue