Category Archives: 12th class

question : what makes glass different from quartz under what conditions quartz is converted into glass ? key points to answer this question : explain the glass property in point of view quartz and then differentiate both glass and Quartz on basis of their properties. solution : Glass is type of an amorphous solid in which the constituent particles like atoms , molecules or may be ions (SiO4 tetrahedra) have only a short range order means they does not consists long order of arrangements of constituent particles . on another […]

question : define the term amorphous with example or amorphous definition and examples class 12 chemistry ? Key points to solve this question : remember the Amorphous word is a Greek word that contains the meaning ‘no form’ it means the Amorphous does not contain any type of form or we can say that they does not contain regular shape so i.e., have irregular shape. Define on this basis and give examples. answer : An amorphous solid are those solids which consists of particles of irregular shape. In amorphous solid, […]

question : a group 14 element is to be converted into n type semiconductor by doping it with a suitable impurity. To which group should this impurity belong ? key points to answer this question : first of all you have to remember that n type semiconductor means there is excess of electrons and due to this excess of electrons the n type semiconductor contains negative charge on it. hence the impurities must be from higher group. solution : N type semiconductor means there is excess of electrons in this […]

Question : Ionic solids , which have anionic vacancies due to metal excess defect , develop colour. Explain with the help of a suitable example ? key points to answer this question : first recall which thing is responsible in solids for colors , so remember the Free unpaired electrons or we can say the F-centres are mainly responsible for the colour of solids. after that we will explain how F-centres are generated in a solids , we will discuss this thing by taking an example of NaCl  with excess […]

question : Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it ? key points to remember answer of this question : first of all Recall the definition of impurity defects occurred in solids with examples also , you have to keep in mind the definition  of impurity defects and their examples and remember , a solid as a whole is neutral in nature. solution : When a cation (positively charged ion) of higher valence is added as […]

question : what type of stoichiometric defect is shown by (i) zns and (ii) agbr key points to remember answer this question : First of all you have to remember that there is very big difference between zns and agbr on the basis of size of ions present in zns and agbr so first we have to think which type of defect can occur on the basis of size of ions. Then also remember the exceptional behavior of AgBr. remember frenkel defect occurs in ionic solids when large difference is […]

question : An element with molar mass 2.7×10-2 kg mol-1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7×103 kg m-3, what is the nature of the cubic unit cell ? Key points to answer this question : First of all we need to calculate the number of atoms present in the unit cell (Z) = Then find the type of the cubic unit cell on the based of number of Z , as follows – If Z = 1 then This will simple cell (SC) […]

Question : Which of the following lattices has the highest packing efficiency – simple cubic lattice body-centred cubic lattice (BCC) hexagonal close-packed lattice (HCP) Key point to answer this question :  Remember the packing efficiency of all lattices asked in our question which are simple cubic , BCC and HCP lattice. then you can easily crake the question in seconds. simple cubic has the packing efficiency = 52.4% body-centred cubic lattice (BCC) has the packing efficiency = 68% hexagonal close-packed lattice (HCP) has the packing efficiency = 74% solution :  […]

Question : A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 1/3rd of tetrahedral voids. What is the formula of the compound ? key points to crake this question : First of all we have to calculate tetrahedral voids present in this lattice , because as we know that the number of tetrahedral voids = 2 x number of atoms present in lattice. now calculate the number of atoms present and then calculate the ratio atoms of M and N […]

Question : A compound forms hexagonal close packed structure.  What is the number of voids in 0.5 mole of it ? how many of these are tetrahedral voids ? key points to answer this question : When asked to calculate the number of voids in hexagonal close packed structure , we have to calculate octahedral and tetrahedral voids , and these voids depends on the number of atoms present in 0.5 mole , that is represent by N , tetrahedral voids are equal to 2N and total voids. Solution : […]