GCE Chemistry inorganic identification tests

CO₂

method: pass through limewater

positive result: colourless > milky ppt > colourless

H₂

method: burning splint in gas sample

Positive result: squeaky pop

O₂

method: place burning splint in gas sample

positive result: splint relights

Cl₂

method: universal indicator paper / litmus paper

positive result: bleaches

NH₃

method: glass rod dipped in conc HCl

positive result: dense white fumes (ui paper blue)

HCl

method: glass rod dipped in conc ammonia

positive result: dense white fumes (ui paper red)

Li⁺

method: dip nichrome wire in conc HCl, touch sample to wire, place in blue bunsen flame

positive result: crimson flame

Na⁺

method: dip nichrome wire in conc HCl, touch sample to wire, place in blue bunsen flame

positive result: orange flame

K⁺

method: dip nichrome wire in conc HCl, touch sample to wire, place in blue bunsen flame

positive result: lilac flame

Ca⁺

method: dip nichrome wire in conc HCl, touch sample to wire, place in blue bunsen flame

positive result: brick red flame

Ba⁺

method: dip nichrome wire in conc HCl, touch sample to wire, place in blue bunsen flame

positive result: green flame

Cu⁺

method: dip nichrome wire in conc HCl, touch sample to wire, place in blue bunsen flame

positive result: blue-green flame

Cl^-

method: add a few drops of dilute nitric acid, add a few cm³ of silver nitrate solution. Add dilute ammonia then conc ammonia

positive result: white ppt > dissolves

Br^-

method: add a few drops of dilute nitric acid, add a few cm³ of silver nitrate solution. Add dilute ammonia then conc ammonia

positive result: cream ppt > remains > dissolves

I^-

method: add a few drops of dilute nitric acid, add a few cm³ of silver nitrate solution. Add dilute ammonia then conc ammonia

positive result: yellow ppt > remains > remains

SO₄^2-

method: add dilute HCl, add a few cm³ of barium chloride

positive result: white ppt

CO₃^2- or HCO₃^-

method: add dilute acid

positive result: effervescence, solid disappears, gas produced: CO₂

NH₄⁺

method: add few cm³ of sodium hydroxide, warm gently

positive result: pungent gas evolved, damp ui paper turns blue, rod dipped in HCl produces white fumes

[Cr(H₂O)₆]³⁺

method: add NaOH _(aq), add excess NaOH_(aq) or excess NH_3(aq)

result: green-blue ppt > green solution > remains

[Mn(H₂O)₆]²⁺

method: add NaOH _(aq), add excess NaOH_(aq) or excess NH_3(aq)

result: white ppt, darkens to brown > remains > remains

[Fe(H₂O)₆]²⁺

method: add NaOH _(aq), add excess NaOH_(aq) or excess NH_3(aq)

result: green > remains > remains

[Mn(H₂O)₆]³⁺

method: add NaOH _(aq), add excess NaOH_(aq) or excess NH_3(aq)

result: brown > remains > remains

[Co(H₂O)₆]²⁺

method: add NaOH _(aq), add excess NaOH_(aq) or excess NH_3(aq)

result: blue > remains > yellow, changes to brown

[Ni(H₂O)₆]²⁺

method: add NaOH _(aq), add excess NaOH_(aq) or excess NH_3(aq)

result: green > remains > blue

[Cu(H₂O)₆]²⁺

method: add NaOH _(aq), add excess NaOH_(aq) or excess NH_3(aq)

result: blue > remains > dark blue

white crystaline solid

not a transition metal compound

group I, group II or ammonium compound

blue crystalline solid

Cu²⁺ or VO²⁺

green crystalline solid

Fe²⁺, Ni²⁺, Cr³⁺, or V³⁺

brown crystalline solid

Fe³⁺

pink crystalline solid

Co²⁺ or Mn²⁺

violet crystalline solid

V²⁺

orange crystalline solid

Cr₂O₇^2-

yellow crystalline solid

CrO₄^2-, VO₂⁺, or VO₃^-

dissolves in water to form colourless solution

group I, group II, Al or NH₄⁺

dissolves in water to form blue solution

Cu²⁺ or VO²⁺

dissolves in water to form green solution

Fe²⁺, Ni²⁺, Cr³⁺ or V³⁺

dissolves in water to form pink solution

Mn²⁺ or Co²⁺

dissolves in water to form yellow solution

CrO₄^2-, VO₂⁺ or VO₃^-

dissolves in water to form orange solution

Cr₂O₇^2-

dissolves in water to form yellow/orange solution

Fe³⁺

dissolves in water to form violet solution

V²⁺

add a few drops of conc H₂SO₄, misty fumes, white smoke with a rod dipped in conc NH₃

Cl^-, fumes are HCl

add a few drops of conc H₂SO₄, misty fumes, red-brown vapour

Br^-, misty fumes are HBr, vapour is Br₂ gas

add a few drops of conc H₂SO₄, misty fumes, purple vapour, smell of rotten eggs, yellow solid, grey-black solid

I^-, misty fumes HI, vapour is I₂, smell is H₂S, yellow solid S, grey-black solid I₂

add a few cm³ of KSCN (potassium thiocyanate) to dissolved sample, blood red solution

Fe³⁺

add a few drops of NaOH to dissolved sample, then add until it is in excess. green ppt, not soluble in excess

Fe²⁺

add a few drops of NaOH to dissolved sample, then add until it is in excess. brown ppt, not soluble in excess

Fe³⁺

add a few drops of NaOH to dissolved sample, then add until it is in excess. green-blue ppt, green solution in excess

Cr³⁺

add a few drops of NaOH to dissolved sample, then add until it is in excess. white ppt that turns brown over time, not soluble in excess

Mn²⁺

add a few drops of NaOH to dissolved sample (blue), then add until it is in excess. blue ppt, not soluble in excess

Cu²⁺

add a few drops of NaOH to dissolved sample (pink), then add until it is in excess. blue ppt, not soluble in excess

Co²⁺

add a few drops of NaOH to dissolved sample, then add until it is in excess. green ppt, not soluble in excess

Ni²⁺

add NaOH to sample, test gas evolved with damp ui paper or a glass rod dipped in conc HCl. Damp ui paper turns blue, white smoke

NH₄⁺

add a few drops of NH_3(aq) to dissolved sample, then add until it is in excess. white ppt that turns brown over time, not soluble in excess

Mn²⁺

add a few drops of NH_3(aq) to dissolved sample, then add until it is in excess. green ppt, not soluble in excess

Fe²⁺

add a few drops of NH_3(aq) to dissolved sample, then add until it is in excess. brown ppt, not soluble in excess

Fe³⁺

add a few drops of NH_3(aq) to dissolved sample, then add until it is in excess. blue ppt, soluble in excess to form yellow solution that darkens to brown over time

Co²⁺

add a few drops of NH_3(aq) to dissolved sample, then add until it is in excess. green ppt, soluble in excess to form blue solution

Ni²⁺

add a few drops of NH_3(aq) to dissolved sample, then add until it is in excess. blue ppt, soluble in excess to form dark blue solution

Cu²⁺

gently heat sample in test tube, colourless liquid forms on walls of tube, change in solid appearance, possible colour change

water of crystallisation present, hydrated salt