identification of unknown compound
EXPERIMENT 1
IDENTIFICATION OF UNKNOWN COMPOUNDS
Date of experiment : 7th August 2012
Venue: ME204
INTRODUCTION
Chemical reactions are regularly categorized into 3 types: oxidation-reduction (redox reaction), precipitation (double displacement) and acid-base reaction (double displacement)
Type 1: Oxidation-Reduction Reactions
Oxidation-reduction processes include the movements of electrons form oxidants to reductants, which lead to increases in oxidation number for oxidised species and decreases in oxidation number in reducing species.
A. Synthesis Reactions: 2 (or more) substances react and product one single substance A + B → AB
B. Decomposition Reactions: a compound turns into 2 or more products (opposite of Synthesis) AB → A + B
C. Single Displacement Reaction: an element takes place another element in a compound to produce new products A + BC => AC + B
Type 2: Double displacement reaction (Precipitation):
In solutions, when two ionic compounds are mixed, exchange ions and form two new products. The reactions can be observed and can be proved to happen through precipations, temperature changes, gas evolution or changes in solutions’ colors.
In some cases when no changes happen, it is considered no reactions occur.
Some general rules:
1
Most nitrate salts are soluble
2
Most salts containing the alkali metal ions and the ammonium ion are soluble
3
Most chloride are soluble in water except AgCl, PbCl2, Hg2Cl2
4
Most compounds containing sulphate are soluble in water, except BaSO4, PbSO4, CaSO4
5
Most compounds containing OH- ion are not soluble in water, except hydroxides of the alkali metal (Group 1A) and Ba(OH)2
6
Others are minorly soluble in water, eg sulphide, carbonate, chromate, phosphate
Type 3: Double Displacement
IDENTIFICATION OF UNKNOWN COMPOUNDS
Date of experiment : 7th August 2012
Venue: ME204
INTRODUCTION
Chemical reactions are regularly categorized into 3 types: oxidation-reduction (redox reaction), precipitation (double displacement) and acid-base reaction (double displacement)
Type 1: Oxidation-Reduction Reactions
Oxidation-reduction processes include the movements of electrons form oxidants to reductants, which lead to increases in oxidation number for oxidised species and decreases in oxidation number in reducing species.
A. Synthesis Reactions: 2 (or more) substances react and product one single substance A + B → AB
B. Decomposition Reactions: a compound turns into 2 or more products (opposite of Synthesis) AB → A + B
C. Single Displacement Reaction: an element takes place another element in a compound to produce new products A + BC => AC + B
Type 2: Double displacement reaction (Precipitation):
In solutions, when two ionic compounds are mixed, exchange ions and form two new products. The reactions can be observed and can be proved to happen through precipations, temperature changes, gas evolution or changes in solutions’ colors.
In some cases when no changes happen, it is considered no reactions occur.
Some general rules:
1
Most nitrate salts are soluble
2
Most salts containing the alkali metal ions and the ammonium ion are soluble
3
Most chloride are soluble in water except AgCl, PbCl2, Hg2Cl2
4
Most compounds containing sulphate are soluble in water, except BaSO4, PbSO4, CaSO4
5
Most compounds containing OH- ion are not soluble in water, except hydroxides of the alkali metal (Group 1A) and Ba(OH)2
6
Others are minorly soluble in water, eg sulphide, carbonate, chromate, phosphate
Type 3: Double Displacement