Question

Why can the physical properties of an unknown substance be used to determine

the identification of the substance?

Design an experiment to determine if your salt is hygroscopic, deliquescent,

efflorescent, or none. Note: this design does not need to be exactly what is followed in

the lab. For full credit, a conscientious effort must be shown in your design.

Answer 1

The Physical properties of compouns depicts their nature of existance,

The description shows the nature of the compound like its amorphous, or crystalline

The solublity properties shows its hydrophilicity and hydrophobicity.

The pH of its solution mention its acidity and alkalinity.

The colour of the compund confirms the basic identification properties of the compound. like CuSO₄ is blue colour compound, NaCl is white colour compound

The state of compound like Solid/Liquid/Gas confirms the class of compounds with its existance properties. Eg.:HCl always in liquid form; KMnO₄ always in solid form,

The odour of Compounds confirms the class of compounds like H₂S which smells like rotten eggs.

The taste of compound is important character to identify the compound primarily

Like: NaCl is salty compound, Glucose is Sweet in taste Disadvantages: Not all compound could be tasted like Acids.

The design of Preliminary test for salt is as per below please refer the same.

Preliminary Test:

1. Colour A. Blue: May be copper salts present B. White: absence of copper salts

2. Appearance:

A. Amorphous: having amorphous nature May be carbonate present

B. Crystalline: Absence of carbonate

C. Efflorescence: these substances when exposed to air, they lose water to the atmosphere e.g. Na2SO4. 10 H2O Na2CO3. 10H2O

D. Hygroscopic: They absorb water from atmosphere when exposed to atmosphere.

e.g. CaO, NaNO3, NaCl, Con. HCl

E. Deliquescence: They absorb enough water to form solutions

e.g.: CaCl2, CaCl2.6H2O, FeCl3, KOH