1. Which of the following is not a characteristic of a crystalline solid?
Answer:
Explanation:
Crystalline solids have a regular and orderly arrangement of particles.
2. In which type of solid are the constituents particles positive ions surrounded by a cloud of electrons?
Answer:
Explanation:
In metallic solids, positive ions are surrounded by a sea of delocalized electrons.
3. Which of the following is an example of a face-centered cubic structure?
Answer:
Explanation:
Copper crystallizes in a face-centered cubic structure.
4. Which type of defect does not change the density of a crystal?
Answer:
Explanation:
In a Frenkel defect, an ion leaves its place to occupy an interstitial site, but it remains within the crystal, so the density remains unchanged.
5. Which one of the following is not a property of amorphous solids?
Answer:
Explanation:
Amorphous solids do not have a definite and sharp melting point.
6. In which of the following is the coordination number 12?
Answer:
Explanation:
In a face-centered cubic structure, each atom has 12 nearest neighbors, hence a coordination number of 12.
7. The voids which are formed in a hexagonal close-packed structure are of which shape?
Answer:
Explanation:
In a hexagonal close-packed structure, the voids formed are tetrahedral.
8. Which defect causes a decrease in the density of a substance?
Answer:
Explanation:
Schottky defect involves the removal of an equal number of cations and anions, leading to a decrease in density.
9. Which of the following solids is best described by van der Waals forces?
Answer:
Explanation:
Iodine is a molecular solid held together by van der Waals forces.
10. The close-packed structures result in the maximum possible ________ in solids.
Answer:
Explanation:
Close-packed structures lead to maximum packing efficiency and hence maximum density.
11. Which of the following is not an example of a covalent or network solid?
Answer:
Explanation:
Ice is a molecular solid, not a covalent or network solid.
12. Which type of solids is soft and can be easily cut with a knife?
Answer:
Explanation:
Molecular solids are typically soft and can be easily cut with a knife due to their weak intermolecular forces.
13. Which of the following defects causes an increase in the density of a crystal?
Answer:
Explanation:
An interstitial defect involves an extra atom occupying an interstitial site, leading to an increase in density.
14. Which one of the following is not a point defect?
Answer:
Explanation:
Grain boundary is a line defect and not a point defect.
15. In a crystal with a simple cubic structure, each atom touches ________ other atoms.
Answer:
Explanation:
In a simple cubic structure, each atom is in contact with six other atoms along the edges.
16. Which of the following is not a characteristic of ionic solids?
Answer:
Explanation:
Many ionic solids are soluble in water due to the strong interactions between ions and water molecules.
17. The number of lattice points in a face-centered cubic (fcc) unit cell is:
Answer:
Explanation:
An fcc unit cell has 8 corner points (1/8th contribution each) and 6 face-centered points (1/2 contribution each), totaling to 4 lattice points.
18. Which of the following is not true for amorphous solids?
Answer:
Explanation:
Amorphous solids do not exhibit a clean cleavage when cut; instead, they break with an irregular fracture.
19. The arrangement of particles in a crystal where the particles are packed in alternating layers of triangles and hexagons is called:
Answer:
Explanation:
In hcp, particles are packed in alternating layers of triangles and hexagons.
20. Which of the following solids will have the highest melting point?
Answer:
Explanation:
Covalent or network solids, like diamond, have strong covalent bonds throughout the entire structure, leading to very high melting points.