Question

(i) Describe indetail one test to distinguish saturated hydrocarbon from unsaturated hydrocarbon.(ii) Describe in detail one test to distinguish ethene 7 and acetylene.

Short answer

Answer: The Bromine Water Test is used to distinguish between saturated and unsaturated hydrocarbons, while the Ammoniacal Cuprous Chloride Test (Copper(I) Chloride Test) is used to distinguish between ethene and acetylene.

Step-by-step solution

Test to Distinguish Saturated and Unsaturated Hydrocarbons

Saturated hydrocarbons contain only single bonds between carbon atoms, while unsaturated hydrocarbons contain either double or triple bonds between carbon atoms. A common test to distinguish these two types of hydrocarbons is the Bromine Water Test. Here is how to carry out the test: Step 1: Prepare Bromine Water Add a few drops of liquid bromine into a test tube containing water until you obtain a yellow-orange solution. Step 2: Add Hydrocarbon Sample Add a few drops of the hydrocarbon being tested to the test tube containing bromine water. Step 3: Observe the Reaction If the hydrocarbon is unsaturated, the bromine water will lose its orange color and become colorless. This is because the bromine reacts with the double or triple bonds in the unsaturated hydrocarbon through an addition reaction. However, if the hydrocarbon is saturated, there will be no color change in the bromine water as it cannot react with single bonds.

Test to Distinguish Ethene and Acetylene

Ethene and acetylene are unsaturated hydrocarbons with a double bond and a triple bond between the carbon atoms, respectively. The test to distinguish between these two compounds is the Ammoniacal Cuprous Chloride Test (also known as the Copper(I) Chloride Test). Here is how to carry out the test: Step 1: Prepare Ammoniacal Cuprous Chloride Solution Dissolve a small amount of cuprous chloride (CuCl) in aqueous ammonia (NH3) in a test tube. The solution should turn deep blue. Step 2: Add Hydrocarbon Sample Pass the gas of the hydrocarbon being tested through the deep blue solution in the test tube. Step 3: Observe the Reaction If the hydrocarbon is ethene, the deep blue color of the solution will remain unchanged, as ethene does not react with the ammoniacal cuprous chloride solution. However, if the hydrocarbon is acetylene, the deep blue color of the solution will turn to a pale blue or colorless because acetylene reacts with the ammoniacal cuprous chloride solution to form a red precipitate of cuprous acetylide (Cu2C2) and the complex Cu(NH3)2Cl. In conclusion, by performing the Bromine Water Test and the Ammoniacal Cuprous Chloride (Copper(I) Chloride) Test, one can distinguish between saturated and unsaturated hydrocarbons and between ethene and acetylene.