Test: Chemistry - 3 - UPSC MCQ

Bleaching powder or calcium hypochlorite is a chemical compound with formula Ca(ClO)₂. The chemical formula for marble is CaCO₃. It is calcium carbonate. Marble is used in various applications, including home design. Gypsum is a very soft sulphate mineral composed of calcium sulphate dihydrate, with the chemical formula CaSO₄ · ₂H₂O. It can be used as a fertilizer, is the main constituent in many forms of plaster and is widely mined.

Manganese is essential to iron and steel production. At present, steel making accounts 85 to 90% of the total demand, most of the total demand. Manganese is a key component of low-cost stainless steel formulations and certain widely used aluminium alloys. Limestone can be used in constructing buildings. It can be used for making cement and mortar. Limestone is used to make glass and even used to make roads. Bauxite is the mineral ore of aluminium which is used in the manufacture of cans, airplanes, sporting and electronic equipment and home appliances. The Wright Brother's first airplane to fly in 1903 only was able to get off the ground because they modified its engine with aluminium in order to reduce its weight. Without the ability of the strong aluminium, alloys to withstand the huge pressures and stresses involved, high altitude flying would not be conceivable. In fact, aluminium comprises about 80% of an aircraft’s unladen weight. The element copper is used extensively as an electrical conductor, for the making of electrical wire.

Fullerene is a pure carbon molecule composed of at least 60 atoms of carbon.

Diamond is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centred cubic crystal structure called a diamond lattice. The most common constituent of sand is silica (silicon dioxide, or SiO₂₎, usually in the form of quartz, which, because of its chemical inertness and considerable hardness, is the most common mineral resistant to weathering. Marble is composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO₃). A ruby is a pink to blood-red-coloured gemstone, a variety of the mineral corundum (aluminium oxide).

The main components of LPG are butane and propane.

The compound is always formed by absorption or evolution of energy but no energy is released or absorbed during the formation of mixture.

Isotopes are variants of a particular chemical element: while all isotopes of a given element share the same number of protons and electrons, each isotope differs from the others in its number of neutrons. For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons, so that the neutron numbers of these isotopes are 6, 7 and 8 respectively

Goldstein discovered proton, ChadwickNeutron, J. J. Thomson- Electron and John DaltonAtomic Theory.

Diamond is an allotrope of carbon not silicon

(i) CO₂ is an acidic oxide. It dissolve in water formic unstable carbonic acid.

(ii) Limewater Ca(OH)₂ is turned milky on passing CO₂

Diamond, an allotrope of carbon, has very high refractive because of which it is used as a gem in jewellery. It is used for cutting glass, marble stones and other hard materials and for drilling of rocks. It is a bad conductor of electricity. It is the hardest material known.

Diamond is hard and bad conductor but Graphite is soft and good conductor.

Nitrogen is a essential constituent of all vegetables and animal proteins. Soil contains nitrogen as ammonium salts.

Both oxygen and moisture present in air cause rusting of iron.

Chlorides and sulphates of calcium and magnesium are responsible for permanent hardness of water. Note: Bicarbonates are responsible for temporary hardness of water.

A homogeneous mixture of two or more metals is known as alloys.

These compounds are used in the manufacture of the following products. Cellulose nitrate- Gun powder, Potassium Sulphate- Fertiliser, Potassium salts of fatty acids- Soft soap, Calcium oxide- Glass.

Electron affinity generally decreases from top to bottom in a group. Atomic radii increases from top to bottom as energy levels increases because as we move down a group number of electrons increases.

When hard boiled egg after shelling is immersed in saturated brine, its size remains same. Due to coagulation of inner liquid there is no flow of solvent molecules across the membrane.

Sodium sulphate and sodium silicate are added to keep the washing powder dry. Sodium triphosphate or sodium carbonate is added to washing powder to maintain the alkalinity.