Chapter 4 Carbon and its Compounds Solutions
Question - 21 : - Why are carbon and its compounds used as fuels for most applications?
Answer - 21 : - Carbon and its compounds used as fuels for most applications for they have high calorific values and give out a lot of energy. Most of the carbon compounds give a lot of heat and light when burnt in air.
Question - 22 : - Explain the formation of scum when hard water is treated with soap?
Answer - 22 : - Scrum is produced from reaction of hard water with soap. Calcium and magnesium present in the hard water form an insoluble precipitate that stick as a white which is also called as scrum.
Question - 23 : - What change will you observe if you test soap with litmus paper (red and blue)?
Answer - 23 : - When we test soap with litmus paper color of litmus paper turns blue from red. As soap is a base it turn red litmus paper into blue.
Question - 24 : - What is hydrogenation? What is its industrial application?
Answer - 24 : - Hydrogenation is a process or a chemical reaction between hydrogen and other compounds. It is usually done in the presence of catalysts: for example nickel, palladium or platinum. Hydrogenation is used mainly to saturate organic compounds.
Question - 25 : - Which of the following hydrocarbons undergo addition reactions: C2H6, C3H8, C3H6, C2H2 and CH4.
Answer - 25 : - Unsaturated hydrocarbons undergo addition reactions. C3H6 and C2H2 are unsaturated hydrocarbons which undergo addition reactions
Question - 26 : - Give a test that can be used to differentiate between saturated and unsaturated hydrocarbons.
Answer - 26 : -
Bromine water test – is used to differentiate between the unsaturated compounds (like alkenes and alkynes) and the saturated compounds. For this purpose, bromine is used in the form of bromine water. A solution of bromine in water is called bromine water. Bromine water has a red-brown color due to the presence of bromine in it. When bromine water is added to an unsaturated compound, then bromine gets added to the unsaturated compound and the red-brown color of bromine water is discharged. So, if an organic compound decolorizes bromine water, then it will be an unsaturated hydrocarbon (containing a double bond or a triple bond), but saturated hydrocarbon (alkanes) do not decolorize bromine water.
Bromine water test is perform to differentiate between the unsaturated compounds (like alkenes and alkynes) and the saturated compounds. Bromine water is added to an un-saturated hydrocarbon red brown color of bromine solution is discharged. Si if there is dis-coloration then the compound will be an unsaturated Hydrocarbon.
Question - 27 : - Explain the mechanism of the cleaning action of soaps.
Answer - 27 : -
There are so many impurities and dirt mixed in water, and most of all the dirt does not dissolve in the water. Soap molecules are a combination of salts such as sodium or potassium. The molecules are of a long chain of carboxylic acids. So, when the carbon chain is dissolved in oil and the ionic end is dissolved in the water, the soap starts cleansing and trapping the dirt. When this happens, the soap molecules form structures that are called micelles are used for capturing the oil droplets and then the other end being the ionic faces. This will then form an emulsion in water and help in dissolving the dirt or impurities when the clothes are washed.
The soap molecules have different properties at different ends. The first end being the hydrophilic end which dissolves in the water and is attracted towards the water and the second one being the hydrophobic end is dissolved in the hydrocarbons and is repulsive to water. The hydrophobic tail aligns itself along the surface of the water because it is not soluble in the water.