31. Which gas is mixed with Oxygen for respiration by divers in deep sea?

1. Helium
2. Nitrogen
3. Xenon
4. Ammonia

Option “A” is correct
Heliox is a breathing gas composed of a mixture of Helium (He) and Oxygen (O2). This is frequently used for respiration by divers in the deep sea.
32. RDX was invented by-

1. Alfred Nobel
2. Soddy
3. Bergillins
4. Henning

Option “D” is correct
RDX, the abbreviation of this word is Research Department Explosive, is also called cyclonite. It is powerful explosive discovered by Georg Friedrich Henning of Germany and patent in 1898 but not used until World War II when most of the warring powers introduced it.
33. The two elements that are frequently used for making transistors are

1. Boron and aluminium
2. Silicon and germanium
3. Iridium and tungsten
4. Niobium and columbium

Option “B” is correct
Silicon and germanium are frequently used for making transistors.
34. Brass gets discoloured in air because of the presence of which of the following gases in air?

1. Oxygen
2. Hydrogen sulphide
3. Carbon dioxide
4. Nitrogen

Option “B” is correct
Brass gets discolored because of the presence of Hydrogen Sulphide in air.
35. In which of the following industries is mica used as a raw material-

1. Iron and steel
2. Toys
3. Glass and pottery
4. Electrical

Option “D” is correct
Mica is good conductor of heat and bad conductor of electricity so mica use in electrical industry.
36. Which of the following is mainly used for the production of Aluminum?

1. Hematite
2. Lignite
3. Bauxite
4. Magnetite

Option “C” is correct
Bauxite is an ore of Aluminum, which is found in the form of Hydrated Aluminium Oxides.
37. Solder used in soldering metal pieces consists of any alloy of:

1. Tin and Zinc
2. Tin and Lead
3. Tin, Zinc and Copper
4. Tin, Lead and Zinc

Option “B” is correct
The common composition of solder is 32% Tin, 68% Lead. This combination has a low melting point and is useful for soldering components that are sensitive to heat.
38. The chemical formula of Heavy Water is?

1. H2O
2. D2O
3. H2CO3
4. H2S

Option “B” is correct
Heavy water Deuterium Oxide is used as a moderator and coolant in nuclear reactors because it slows down neutrons effectively and also has a low probability of absorption of neutrons.
39. The atomic nucleus was discovered by:

1. Rutherford
2. Dalton
3. Einstein
4. Thompson

Option “A” is correct
The nucleus is a very dense region consisting of protons and neutrons at the centre of an atom. It was discovered in 1911 as a result of Ernest Rutherford’s interpretation of the 1909 Geiger-Marsden gold foil experiment.
40. Which of the following method is used for measuring the age of the earth?

1. Iron dating process
2. Biotechnology Law
3. Biological clock method
4. Uranium process

Option “D” is correct
Uranium-lead dating is one of the oldest and most refined methods to determine the age of the earth, decaying rocks and bones.
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178 thoughts on “Chemistry”

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