identification of unknown compound

Topics: Chemical reaction, Chemical reactions, Chemistry Pages: 5 (874 words) Published: April 8, 2014


Date of experiment : 7th August 2012
Venue: ME204

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:
Most nitrate salts are soluble
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 Reactions (Acid-Base Reactions): The products of reactions between acids and bases are normally salt and water. In additional, sometime gas will be involved in this type of reactions. Heat will be release, which increases the temperature of the solution if neutralisation happens. (A) Acid + basic hydroxide => Salt + water

(B) Acid + basic carbonate => Salt + water + CO2
(C) Acid + basic oxide => Salt + water
Stoichiometry and Law of Conservation Mass
Stoichiometry – a field of chemistry working with the weight relations between atoms in a molecule or compounds in a chemical reaction, root from the law of conservation of mass and the law of definite proportions. The relationship mentioned can be verdicted from balanced chemical equation. The realistic yield of products collected by weighing is normally different from the theoretical yield due to experimental errors. The formula for comparison is shown below: Percentage of yield = (Actual yield) : (Theoretical yield) x 100%

The main objective of these experiments is to find the name of 6 solutions/subtances A,B,C,D,E,F. The method will be used to determine the solutions is basically is testing solutions with a chosen reagent and observe the changes based on 3 types of chemical reactions. Another method involves is the formula based on Stoichiometry and Law conservative mass; also the formula for comparison: Percentage of yield = (Actual yield) : (Theoretical yield) x 100% Furthermore, the objective of these experiments is also to understand the proper, accurate and safe way to conduct the experiments. Include part B


Task A: Procedure to identify the unknown chemical
Of all the substances given, copper (II) nitrate is the only substance that is blue (*) found copper (II) nitrate
Take each of unknown substances and put in labeled testtubes with the amount of 10ml each...
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