There is Case Study Questions in class 12 Chemistry in session 2020-21. The first two questions in the board exam question paper will be based on Case Study and Assertion & Reason. The first question will have 5 MCQs out of which students will have to attempt any 4 questions. The second question will carry 5 Assertion & Reason type questions with the choice to attempt any four. Here are the questions based on case study.
Case Study Question 1:
Read the passage given below and answer the following questions:
The adjective, ‘crystalline’ when applied to solids, implies an ideal crystal in which the structural units, termed as unit cells, are repeated regularly and indefinitely in three dimensions in space. The unit cell, containing at least one molecule has definite orientation and shape defined by the translational vectors, a, b and c. The unit cell therefore has a definite volume, V that contains the atoms and molecules necessary for generating the crystal. Every crystal can be classified as a member of one of the seven possible crystal systems or crystal classes that are defined by the relationship between the individual dimensions, a, b and c of the unit cell and between the individual angles, α, β, and γ of the unit cell. The structure of the given crystal may be assigned to one of the 7 crystal systems, to one of the 14 Brevais lattices, and to one of the 230 space groups. This uniquely define the possible ways of rearranging atoms in a three-dimensional solid, Based on these observations, seven crystal systems were identified: triclinic, monoclinic, trigonal or rhombohedral, tetragonal, hexagonal, rhombic or orthorhombic and cubic.
The following questions are multiple choice questions. Choose the most appropriate answer:
(1) The crystal system of a compound with unit cell dimensions, a=0.387 nm, b=0.387 nm and c=0.504 nm and α = β = 900 and γ=1200 is
(2) The unit cell with the structure given below represents ________crystal system.
(3) In a triclinic crystal
(a) a = b = c, α = β = γ ≠ 900
(b) a ≠ b = c, α = β = γ = 900
(c) a ≠ b ≠ c, α ≠ β ≠ γ ≠ 900
(d) a ≠ b ≠ c, α = γ = 900 , β ≠ 900
(4) The unit cell with dimensions α = β = γ = 900 , a = b ≠ c is
An example of orthorhombic crystal system is