Question

Share

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 a 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 relationships between the individual dimensions, a, b and c of the unit cell and between the individual angles, ⁣$\alpha,\beta$ and $\gamma$ of the unit cell. The structure of the given crystal may be assigned to one of the $7$ crystal systems, to one of the $14$ Bravais lattices, and to one of the 230 space groups. These uniquely define the possible ways of arranging 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 = 0.38$7nm, $b = 0.387$nm and $c = 0.504$nm $\alpha=\beta=90^\circ$ and $\gamma=120^\circ$ is.

1. Cubic
2. Hexagonal
3. Orthorhombic
4. Rhombohedral.

2. The unit cell with the structure given below represents________________crystal system.

1. Cubic
2. Orthorhombic
3. tetragonal
4. trigonal

3. In a triclinic crystal.

1. $\text{a}=\text{b}=\text{c},\ \alpha=\beta=\gamma\neq90^\circ$
2. $\text{a}\neq\text{b}=\text{c},\ \alpha=\beta=\gamma=90^\circ$
3. $\text{a}\neq\text{b}\neq\text{c},\ \alpha\neq\beta\neq\gamma\neq90^\circ$
4. $\text{a}\neq\text{b}\neq\text{c},\ \alpha=\gamma=90^\circ\beta\neq90^\circ$

4. The unit cell with dimensions $\alpha=\beta=\gamma=90^\circ,\ \text{a}=\text{b}\neq\text{c}$ is.

1. Cubic
2. Triclinic
3. Hexagonal
4. Tetragonal.

5. An example of orthorhombic crystal system is.

1. $SnO_2$
2. $KN0_3$
3. $ZnO$
4. $K_2Cr_2O_7$