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Directions: Study the following questions carefully and choose the right answer.
» Explain it
Sublimation is one of the methods of separation of mixtures. During sublimation, a solid substance directly passes into its vapors, on application of heat. The vapors upon cooling give back original substance. Some example of sublimes are- Naphthalene, Iodine, Ammonium Chloride etc.

Hence, option A is correct.
What is the true value of Avogadro’s number?
» Explain it
Avogadro constant or Avogadro’s number us the number of particles in a mole. It is named after the famous scientist Amedeo Avogadro and its value is 6.023×1023.

Hence, option D is correct.
Isotones are atoms of different elements having a same number of ________?
» Explain it
Fundamental particles of an atom are Electron, proton and neutron. Neutron had been discovered by James Chadwick. It has zero charge and mass 1.00863 amu. Isotones are atoms of different elements having the same number of neutrons. 146C, 157N,168O.

Hence, option C is correct.
» Explain it
Classification of elements entails the arrangement of the known elements in certain groups in such a away so that elements with similar properties are grouped together. Mendeleev is considered as the father of periodic table. He gave a law according to which the physical and chemical properties of the elements are the periodic function of their atomic masses. Base on this the periodic table was tabulated.

Hence, option B is correct.
Which of the following is not a popular use of HCl(Hydrochloric Acid)?
» Explain it
Hydrochloric acid is a colorless and odorless solution of hydrogen chloride and water; with chemical formula HCl. It is used in digestion. Apart from that it is also used in
  • As a bathroom cleaner
  • As a pickling agent before galvanization
  • In leather tanning industry
  • In dying and textile industry
  • In manufacturing gelatin from bones

Sulphuric acid is used in manufacturing of alum.