Chemistry (CDS-Solved Paper)

The white material is Plaster of Paris. It is calcium sulphate hemihydrate
It is used for setting fractured bones. When mined with water, it takes up the water of crystallisation and sets into a hard mass.

Optical instrument are made up of hard glass. It is also known as potash glass. It is prepared by passing a mixture of potassium carbonate and silica. As its name indicates, it is very hard and have high melting point.

Biogas is a type of biofuel that is naturally produced from the decomposition of organic waste. When organic matter, such as food scraps and animal waste, break down in an anaerobic environment (an environment absent of oxygen) they release a blend of gases, primarily methane and carbon dioxide.
Because this decomposition happens in an anaerobic environment, the process of producing biogas is also known as anaerobic digestion.
Biogas Composition
● Methane - 50-74%, CO₂ - 25-50%
● Nitrogen - 0-10%, Hydrogen - 0-1%
● Hydrogen sulphide - 0-3%, oxygen - 0-2%
Hence, option (b) is correct answer.

Carbon credit is a generic term for any tradable certificate or permit representing the right to emit one tonne of carbon dioxide or the mass of another greenhouse gas with a carbon dioxide equivalent to one tonne of carbon dioxide.

An emulsion is a dispersion of finely divided droplets in another liquid. Thus, these are liquid-liquid ‘colloidal systems. Generally, one of two liquids is water and the other, which is immiscible with water, is designated as oil.

Strontium-90, iodine-131 and cesium-137, all three are radioactive substances that enters the human body through food chain and causes many physiological disorders in all form of individuals involved in food chain.

When a pressure, more than the osmotic pressure is applied to the solution, the solvent may pass from solution into the solvent through the semi-permeable membrane. This type of osmosis is known as reverse osmosis. Reverse osmosis is used for the desalination of sea water. Hence, option (a) is true.

A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Because of their broad range of properties, both synthetic and natural polymers play essential ubiquitous role in everyday life. All the polymers except rubber contain glucose units.

Tincture of iodine, iodine tincture or weak iodine solution is an antiseptic.
It is usually 2-7% elemental iodine, along with potassium iodide or sodium iodide, dissolved in a mixture of ethanol and water. Tincture solutions are characterised by the presence of alcohol.