- electrons absorb energy from the flame - they move into a higher energy level - as they move back down, they release the energy as specific wavelengths of light

Inorganic chemistry Flashcards by Nijel Manalo

Why ionisation energy decreases down group 2

more electron shielding
larger atomic radius
less attraction between nucleus and outer shell

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Why reactivity increases down group 2

metals lose electrons in reactions
shielding and atomic radius increase
it becomes easier to lose electrons

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Group 2 reaction with oxygen

Group 2 + oxygen&raquo_space; group 2 oxide

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Group 2 reaction with chlorine

Group 2 + chlorine&raquo_space; group 2 chloride

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Group 2 reaction with water

Group 2 + water&raquo_space; group 2 hydroxide + hydrogen

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Group 2 oxide reaction with water

Group 2 oxide + water&raquo_space; group 2 hydroxide

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Group 2 oxide / hydroxide reaction with dilute acid

Group 2 oxide / hydroxide + acid&raquo_space; group 2 salt + water

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Solubility of group 2 sulfates down the group

Decreases (remember insoluble barium sulfate precipitate from the test for sulfates)

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Solubility of group 2 hydroxides down the group

Increases (magnesium hydroxide can be used as medicine because of its low solubility)

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Explain the trend in thermal stability of metal carbonates and nitrates

thermal stability decreases as polarising power of the cation increases (size decrease, charge increase)
as the anion’s electrons are distorted, its covalent bonds become weaker

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How flame tests work

electrons absorb energy from the flame
they move into a higher energy level
as they move back down, they release the energy as specific wavelengths of light

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How to do a flame test

dip nichrome wire into concentrated HCl then into the solid sample
hold the wire over a flame and observe the colour

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How to test thermal stability of nitrates

heat the nitrate
normal decomposition gives no observation
greater decomposition (so a less stable nitrate) produces brown fumes (nitrogen dioxide)

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How to test thermal stability of carbonates

weigh the sample of carbonate
heat it
weigh the sample again
if mass decreased, decomposition occurred (so a less stable carbonate)

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Lithium flame

Red

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Sodium flame

Yellow

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Potassium flame

Lilac

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Rubidium flame

Purple

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Caesium flame

Blue

Calcium flame

Orange

Strontium flame

Crimson

Barium flame

Apple green

Why boiling point increases down group 7

amount of electrons increases

- london forces become stronger

Why electronegativity decreases down group 7

electron shielding increases
atomic radius increases
less attraction between nucleus and bonding electron pairs

Why reactivity decreases down group 7

- halogens want to gain electrons in a reaction - shielding and atomic radius increase - it becomes harder to gain electrons

Displacement redox reactions of halogens

A more reactive halogen displaces and oxidises a less reactive halide ion

Why is cyclohexane added to identify halogens?

- it is hard to tell the difference between halogens in aqueous solution - halogens are more soluble in organic solvent and the colour difference is clearer

Chlorine in cyclohexane

Pale green (same as in water)

Bromine in cyclohexane

Orange (same as in water)

Iodine in cyclohexane

Purple (changed from brown in water)

Disproportionation of chlorine with water

- chlorine + water >> hydrochloric acid + chloric(i) acid - Cl reduced from 0 to -1 in HCl - Cl oxidised from 0 to +1 in HClO - reaction is used to disinfect water

Reduction of halogens with metal

- metal + halogen >> metal halide | - halogen reduced from 0 to -1 in the metal halide

Disproportionation of chlorine with cold, dilute sodium hydroxide

- chlorine + sodium hydroxide >> sodium chloride + sodium chlorate(i) + water - Cl reduced from 0 to -1 in NaCl - Cl oxidised from 0 to +1 in NaClO - reaction is used to make bleach (NaClO)

Disproportionation of chlorine with hot, concentrated sodium hydroxide

- chlorine + sodium hydroxide >> sodium chloride + sodium chlorate(v) + water - Cl reduced from 0 to -1 in NaCl - Cl oxidised from 0 to +5 in NaClO3 - reaction is used to make weed killer (NaClO3)

Oxidation number of sulfur in sulfuric acid

Oxidation number of sulfur in sulfur dioxide

Oxidation number of sulfur in hydrogen sulfide

-2

Reactions of halide ions with sulfuric acid

Halide ions act as reducing agents for sulfur: Chloride - sulfur dioxide produced Bromide - sulfur dioxide and sulfur Iodide - sulfur dioxide, sulfur, and hydrogen sulfide Reducing power increases down the group

Test for chloride ions

Add silver nitrate - white precipitate | Add dilute ammonia - solid dissolves

Test for bromide ions

Add silver nitrate - cream precipitate Add dilute ammonia - solid does not dissolve Add concentrated ammonia - dissolves

Test for iodide ions

Add silver nitrate - yellow precipitate Add dilute ammonia - solid does not dissolve Add concentrated ammonia - still does not dissolve

Reactions of hydrogen halides

- hydrogen halide + water >> acidic solution | - hydrogen halide + ammonia >> ammonium halide salt

Test for carbonate / hydrogencarbonate ions

- react with dilute acid - colourless gas (carbon dioxide) is produced - white precipitate when gas is bubbled through limewater

Test for sulfate ions

- react with acidified barium chloride | - white precipitate (barium sulfate) produced

Test for ammonium ions

- heat with dilute sodium hydroxide - colourless gas (ammonia) is produced - gas causes damp red litmus paper to turn blue