Physical Analysis

Salt	Colour of solid	Colour of Aqueous salt solution
Salts containing $\text{Na}^+$ , $\text{K}^+$ , $\text{Ca}^{2+}$ , $\text{Mg}^{2+}$ , $\text{Al}^{3+}$ , $\text{Zn}^{2+}$ , $\text{NH}_4^+$	White	Colourless
$\text{CuSO}_4$ , $\text{Cu(NO}_3)_2$	Blue (Hydrated salts)	Blue
$\text{CuCl}_2$	Green	Blue
$\text{CuCO}_3$	Green	insoluble
$\text{FeSO}_4$ , $\text{Fe(NO}_3)_2$ , $\text{FeCl}_2$	Green	Green
$\text{FeCl}_3$	Brown	Yellow
$\text{PbO}$	Yellow when hot and red when cold	insoluble
$\text{CuO}$	Black	insoluble
$\text{ZnO}$	Yellow when hot and white when cold	insoluble
$\text{PbCl}_2$	White	Insoluble in cold water, but soluble in hot water to give a colourless solution
$\text{PbI}_2$	Yellow	Insoluble in cold water but soluble in hot water to give a colourless solution

Chemical Analysis

Cations

Sodium Hydroxide

Ions	Observations	<
	Add $\ce{NaOH(aq)}$ dropwise	Add $\ce{NaOH(aq)}$ until in excess
$\ce{Ca^2+}$	A white precipitate of $\ce{Ca(OH)2(s)}$ was formed. $\ce{Ca^2+(aq) + 2OH^-(aq) -> Ca(OH)2(s)}$	White precipitate was insoluble in excess $\ce{NaOH(aq)}$
$\ce{Zn^2+}$	A white precipitate of $\ce{Zn(OH)2(s)}$ was formed. $\ce{Zn^2+(aq) + 2OH^-(aq) -> Zn(OH)2(s)}$	White precipitate was soluble in excess $\ce{NaOH(aq)}$ to give a colourless solution (zincate ions). $\ce{Zn(OH)2(s) + 2OH^-(aq) -> Zn(OH)4^2-(aq)}$
$\ce{Al^3+}$	A white precipitate of $\ce{Al(OH)3(s)}$ was formed. $\ce{Al^3+(aq) + 3OH^-(aq) -> Al(OH)3(s)}$	White precipitate was soluble in excess $\ce{NaOH(aq)}$ to give a colourless solution (aluminate ions). $\ce{Al(OH)3(s) + OH^-(aq) -> Al(OH)4^-(aq)}$
$\ce{Pb^2+}$	A white precipitate of $\ce{Pb(OH)2(s)}$ was formed. $\ce{Pb^2+(aq) + 2OH^-(aq) -> Pb(OH)2(s)}$	White precipitate was soluble in excess $\ce{NaOH(aq)}$ to give a colourless solution (plumbate ions). $\ce{Pb(OH)2(s) + 2OH^-(aq) -> Pb(OH)4^2-(aq)}$
$\ce{Fe^2+}$	A green precipitate of $\ce{Fe(OH)2(s)}$ was formed. $\ce{Fe^2+(aq) + 2OH^-(aq) -> Fe(OH)2(s)}$	Green precipitate was insoluble in excess $\ce{NaOH(aq)}$
$\ce{Fe^3+}$	A red-brown precipitate of $\ce{Fe(OH)3(s)}$ was formed. $\ce{Fe^3+(aq) + 3OH^-(aq) -> Fe(OH)3(s)}$	Red-brown precipitate was insoluble in excess $\ce{NaOH(aq)}$
$\ce{Cu^2+}$	A blue precipitate of $\ce{Cu(OH)2(s)}$ was formed. $\ce{Cu^2+(aq) + 2OH^-(aq) -> Cu(OH)2(s)}$	Blue precipitate was insoluble in excess $\ce{NaOH(aq)}$
$\ce{NH4^+}$	No precipitate formed. $\ce{NH4^+(aq) + OH^-(aq) -> NH3(g) + H2O(l)}$ Note: Colourless and pungent gas which turns damp red litmus paper blue is formed upon heating. Ammonia gas ( $\ce{NH3}$ ) evolved.	Not Applicable.

Aqueous ammonia

Ions	Observations
	Add $\ce{NH3(aq)}$ dropwise	Add $\ce{NH3(aq)}$ until in excess
$\ce{Ca^2+}$	No precipitate formed.	Not Applicable.
$\ce{Zn^2+}$	A white precipitate of $\ce{Zn(OH)2(s)}$ was formed. $\ce{Zn^2+(aq) + 2OH^-(aq) -> Zn(OH)2(s)}$	White precipitate was soluble in excess $\ce{NH3(aq)}$ to give a colourless solution. $\ce{Zn(OH)2(s) + 4NH3(aq) -> Zn(NH3)4^2+(aq) + 2OH^-(aq)}$
$\ce{Al^3+}$	A white precipitate of $\ce{Al(OH)3(s)}$ was formed. $\ce{Al^3+(aq) + 3OH^-(aq) -> Al(OH)3(s)}$	White precipitate was insoluble in excess $\ce{NH3(aq)}$ .
$\ce{Pb^2+}$	A white precipitate of $\ce{Pb(OH)2(s)}$ was formed. $\ce{Pb^2+(aq) + 2OH^-(aq) -> Pb(OH)2(s)}$	White precipitate was insoluble in excess $\ce{NH3(aq)}$ .
$\ce{Fe^2+}$	A green precipitate of $\ce{Fe(OH)2(s)}$ was formed. $\ce{Fe^2+(aq) + 2OH^-(aq) -> Fe(OH)2(s)}$	Green precipitate was insoluble in excess $\ce{NH3(aq)}$ .
$\ce{Fe^3+}$	A red-brown precipitate of $\ce{Fe(OH)3(s)}$ was formed. $\ce{Fe^3+(aq) + 3OH^-(aq) -> Fe(OH)3(s)}$	Red-brown precipitate was insoluble in excess $\ce{NH3(aq)}$ .
$\ce{Cu^2+}$	A blue precipitate of $\ce{Cu(OH)2(s)}$ was formed. $\ce{Cu^2+(aq) + 2OH^-(aq) -> Cu(OH)2(s)}$	Blue precipitate was soluble in excess $\ce{NH3(aq)}$ to give a dark blue solution. $\ce{Cu(OH)2(s) + 4NH3(aq) -> Cu(NH3)4^2+(aq) + 2OH^-(aq)}$
$\ce{NH4^+}$	No precipitate formed.	Not Applicable.

Other tests

Further Tests for Cations

Dilute $\ce{H2SO4}$ $\ceH2SO4$ Test
- White precipitate indicates $\ce{Ba^2+}$ or $\ce{Pb^2+}$ due to formation of insoluble $\ce{BaSO4}$ or $\ce{PbSO4}$
Dilute $\ce{HCl}$ $\ceHCl$ Test
- White precipitate indicates $\ce{Pb^2+}$ $\cePb2+$ due to insoluble $\ce{PbCl2}$ $\cePbCl2$ formation
  - Precipitate will be soluble upon heating as increase in temperature enhances solubility
  - Heating causes solution to become saturated, and upon heating, white crystals will appear
Aqueous $\ce{KI}$ $\ceKI$ Test
- Yellow precipitate indicates $\ce{Pb^2+}$ due to formation of insoluble $\ce{PbI2}$ , which dissolves on heating and forms yellow crystals upon cooling
- White precipitate in a brown solution indicates $\ce{Cu^2+}$ $\ceCu2+$ where $\ce{Cu^2+}$ $\ceCu2+$ is reduced to $\ce{Cu^+}$ $\ceCu+$ and $\ce{I^-}$ $\ceI−$ is oxidised to $\ce{I2}$ $\ceI2$
  - $\ce{2Cu^2+(aq) + 4I^-(aq) -> Cu2I2(s) + I2(aq)}$
- Brown solution alone indicates an oxidising agent like $\ce{Fe^3+}$ $\ceFe3+$ where $\ce{Fe^3+}$ $\ceFe3+$ is reduced to $\ce{Fe^2+}$ $\ceFe2+$ and $\ce{I^-}$ $\ceI−$ is oxidised to $\ce{I2}$ $\ceI2$
  - $\ce{2Fe^3+(aq) + 2I^-(aq) -> 2Fe^2+(aq) + I2(aq)}$
Acidified aqueous $\ce{KMnO4}$ $\ceKMnO4$ / $\ce{K2Cr2O7}$ $\ceK2Cr2O7$ Test
- Tests for reducing agents like $\ce{Fe^2+}$ $\ceFe2+$ , which are oxidised to $\ce{Fe^3+}$ $\ceFe3+$
  - Purple $\ce{KMnO4}$ solution is decolourised
  - orange $\ce{K2Cr2O7}$ solution turns green

Anions

Ions	Reagent used	Observations
$\ce{CO3^{2-}}$	Add dilute $\ce{HNO3(aq)}$ or any other mineral acid to $1\text{ cm}^3$ of the unknown. Test the gas evolved using limewater.	Effervescence of a colourless and odourless gas, which gave a white precipitate with limewater. The gas is $\ce{CO2}$ . $\ce{2H+(aq) + CO3^{2-}(aq) -> CO2(g) + H2O(l)}$
$\ce{Cl^-}$	Add dilute $\ce{HNO3(aq)}$ , followed by aqueous silver nitrate solution.	White precipitate of $\ce{AgCl(s)}$ was formed. $\ce{Ag+(aq) + Cl^-(aq) -> AgCl(s)}$
$\ce{I^-}$	Add dilute $\ce{HNO3(aq)}$ , followed by aqueous silver nitrate solution. Confirmation Test: Add dilute $\ce{HNO3(aq)}$ , followed by aqueous lead (II) nitrate solution (not used in the lab).	Yellow precipitate of $\ce{AgI(s)}$ was formed. $\ce{Ag+(aq) + I^-(aq) -> AgI(s)}$ Yellow precipitate of $\ce{PbI2(s)}$ was formed. $\ce{Pb^{2+}(aq) + 2I^-(aq) -> PbI2(s)}$
$\ce{SO4^{2-}}$	Add dilute $\ce{HNO3(aq)}$ followed by aqueous barium nitrate or aqueous barium chloride solution.	White precipitate of $\ce{BaSO4(s)}$ was formed. $\ce{Ba^{2+}(aq) + SO4^{2-}(aq) -> BaSO4(s)}$
$\ce{NO3^-}$	Add $\ce{NaOH(aq)}$ followed by aluminium powder/foil. Warm carefully. Test the gas evolved using a damp red litmus paper.	Colourless and pungent gas was evolved which turned the damp red litmus paper blue. Gas evolved is $\ce{NH3(g)}$ . $\ce{8Al(s) + 3NO3^-(aq) + 5OH^-(aq) + 18H2O(l) -> 3NH3(g) + 8[Al(OH)4]^-(aq)}$

Gases

Ions	Reagent used	Observations
$\ce{CO2}$	Test the gas evolved using limewater ( $\ce{Ca(OH)2(aq)}$ ).	Colourless, odourless gas evolved that gave a white precipitate with limewater. $\ce{CO2(g) + Ca(OH)2(aq) -> CaCO3(s) + H2O(l)}$
$\ce{NH3}$	Test the gas evolved with damp red litmus paper.	Colourless, pungent gas evolved that turned damp red litmus paper blue.
$\ce{Cl2}$	Test the gas evolved with damp litmus paper.	Greenish yellow, pungent gas evolved that turned damp blue litmus paper red, and then bleached it.
$\ce{H2}$	Test with a lighted splint.	Colourless, odourless gas evolved that extinguished the lighted splint with a 'pop' sound.
$\ce{O2}$	Test with a glowing splint.	Colourless, odourless gas evolved that relights the glowing splint.
$\ce{SO2}$	Test gas evolved with acidified potassium manganate(VII), $\ce{KMnO4}$	Colourless, pungent gas evolved that turned purple $\ce{KMnO4}$ solution colourless.
$\ce{NO2}$		Pungent, brown gas