Colour and chemistry reactions

ZnO solid colour

Yellow when heated, turns white when cooled

FeO solid

Black solid with yellow sparks given during heating

PbO

Orange when heated, yellow when cooled

Fe2O3 solid

Look reddish brown when heated

CuO solid

Black

K2Cr2O7 solid

Orange

NO2 gas

Brown

Br2 in room temperature

reddish brown liquid

Br2 dissolved in organic solvents

Orange

Br2 aq

Yellowish-brown

Br2 at high temperature

Reddish brown gas

I2 at room temperature

Black solid

I2 dissolved in organic solvents

Purple

I2 aq

Brown

I2 at high temperature

Purple gas

With these three cations, everything is soluble

Na+, K+, NH4+

With these two anions, everything is soluble

NO3-, HCO3-

Halide ions EG Cl-, I-, Br- are MOSTLY SOLUBLE except for….

Halides paired with Ag+ or Pb2+ (EG AgCl2 PbI2) are insoluble

Cmpds paired with SO4 2- sulphate are MOSTLY SOLUBLE except for….

BaSO4, PbSO4, CaSO4 => white precipitate

Cmpds with CO3 2- carbonate are MOSTLY INSOLUBLE except for

K2CO3, Na2CO3, (NH4)2CO3

Cmpds with O2- oxide are MOSTLY INSOLUBLE except

Na2O, K2O, CaO (quicklime), MgO

When Iodine is heated

Black solid sublimes (s → g) and purple vapour evolves

When NH4Cl (s) Ammonium chloride is heated

White solid sublimes (Heated NH4Cl turns into NH3 and HCl, but the two gases when cooled decompose back into NH4Cl)

flame test NH4+ Ammonium ion

Upon warming, it gives off a gas with a pungent smell which turns moist red litmus paper blue

K+ flame test

Lilac flame

Na+

Golden yellow flame

Ca2+ flame test

Brick-red flame

Ca2+ test with NaOH

white precipitates form (Ca(OH)2 slacked lime)

Chemical test for Ca2+ or Ba2+

Add dilute sulphuric acid, white precipitates are formed (Ca(OH)2, Ba(OH)2)

Zn2+ with NaOH

Zn(OH)2, white precipitates are formed, will dissolve in excess NaOH to give a colourless solution [Zn(OH)4]2-（圓裏星）

Zn2+ Add NH3 (aq)

Zn(OH)2, white precipitates are formed, precipitates will will redissolve in excess NH3 aq to give a colourless solution [Zn(NH3)4]2+ aq (星級銀）

Al3+ add NaOH

White precipitates are formed Al(OH)3, precipitates will redissolve in excess NaOH to give a colourless solution [Al(OH)4]- aq 圓裏星

All cations except for Zn2+, Cu2+, Ag+ when reacting with NH3 aq

White precipitates are formed