Q1: Red phosphorous is changed into white phosphorous by

ANS:C - vaporisation followed by condensation.

Red phosphorus is not changed into white phosphorus by any of the methods mentioned. Red phosphorus and white phosphorus are two allotropes of phosphorus, meaning they are different forms of the same element. The conversion of red phosphorus into white phosphorus is not a reversible process, and it does not occur simply by heating in the presence of light, melting under pressure, or vaporization followed by condensation. Red phosphorus is a more stable form of phosphorus, and it is typically obtained by heating white phosphorus in the absence of air or by exposing white phosphorus to sunlight. White phosphorus, on the other hand, is obtained through various methods, including the heating of phosphate rock with carbon and silica, followed by reduction with carbon. The transformation of white phosphorus into red phosphorus involves a change in the arrangement of atoms, resulting in different physical and chemical properties. Therefore, the conversion of red phosphorus into white phosphorus or vice versa requires specific chemical processes rather than simple physical changes.