Chemistry MCQs

Notes:
Sulphur is used in vulcanization of rubber. Its effective and fast link in form of cross-links to rubber macromolecules. Uncured natural rubber is sticky, deforms easily when warm, and is brittle when cold. In this state it cannot be used to make articles with a good level of elasticity.

Notes:
Hydrogen has the highest calorific value as it releases about 150 kilojoules (kJ) of energy per gram. This is nearly three times the energy yield of methane. It is often utilized in its liquid state because of its exceptional energy efficiency, especially in space exploration. The calorific value of coal is significantly less, which is then followed by wood, whose calorific value stands at a low 17 kJ/g.

Notes:
Gypsum is a mineral and is hydrated calcium sulfate in chemical form. It plays a very important role in controlling the rate of hardening or setting of the cement. If not added, the cement would set instantaneously upon addition of water leaving no time for concrete placing and compaction. It helps in prolonging the setting time of cement.

Notes:
Gypsum is a non-metallic mineral. Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO₄· 2H₂O. It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard/sidewalk chalk, and drywall.

Notes:
Amedeo Avogadro (1776 – 1856) was an Italian scientist who came up with Avogadro’s law which states that equal volumes of all gases contain the same number of molecules when under the same conditions of pressure and temperature. The Avogadro constant was named after him.

Notes:
Marie Curie (1867-1934) was a Polish chemist who coined the term radioactivity. She also discovered the elements polonium and radium. She was the first woman to win the Nobel Prize and won the award twice, once for physics in 1903 and again for chemistry in 1911. The unit for measuring radioactivity, the Curie, is named after her and her husband Pierre.

Notes:
Common indicators, like litmus, methyl orange and phenolphthalein easily detect whether a solution is acidic or alkaline, but they cannot easily determine how much a given acidic solution is stronger than another acidic solution. It means they cannot really tell us the pH value of different acidic or alkaline solutions. In case of litmus, we cannot tell about pH values of 5, 6 and 7. Similarly, in case of methyl orange pH values between 3 and 8 will not be very accurate.

Notes:
Baking soda is chemically sodium bicarbonate (NaHCO₃) which does not contain any water of crystallization.

Notes:
Tungsten is the metal with highest melting point of 3422 degree centigrade. Top 5 metals with highest melting point are given here:

Metal	Melting Point (°C)	Melting Point (°F)
Tungsten (W)	3422	6192
Rhenium (Re)	3186	5767
Osmium (Os)	3033	5491
Tantalum (Ta)	3017	5463
Molybdenum (Mo)	2623	4753

Notes:
Natural rubber contains the polymers mof isoprene. Polymers are the substances whose molecular structure comprises of large number of identical units.