Solid State

In KCl (potassium chloride) crystal, ionic defects can occur due to the misplacement or absence of ions in the crystal structure. Let's analyze each option:
- Schottky defect (A): The Schottky defect is a vacancy defect that occurs when equal numbers of cations and anions are missing from the lattice. This type of defect reduces the density of the crystal, and is commonly found in KCl.
Therefore, KCl shows a Schottky defect.
- Frenkel defect (B): The Frenkel defect occurs when an ion (usually a cation) is displaced from its normal position and occupies an interstitial site. This defect is also possible in KCl, but it is more commonly seen in AgCl and ZnS. KCl does exhibit Frenkel defects to some extent, though they are less common compared to Schottky defects.
- Metal excess defect (C): In a metal excess defect, extra metal cations are added to the crystal and occupy interstitial positions, usually to balance the charge. KCl does not exhibit this defect under normal conditions.
- Metal deficiency defect (D): In a metal deficiency defect, there is a lack of metal cations in the crystal. KCl does not typically show metal deficiency defects under normal conditions.
Thus, the correct answer is Option (1), as KCl can exhibit both Schottky defects and Frenkel defects.
Reactions for Defects: - Schottky defect: The Schottky defect occurs due to the removal of equal numbers of cations and anions from the lattice: - Frenkel defect: The Frenkel defect occurs when a cation is displaced to an interstitial site:

To determine which compound shows metal excess defect due to anionic vacancy, we need to examine the nature of defects in each option:

• ZnO: Upon heating, zinc oxide (ZnO) loses oxygen, resulting in an oxygen vacancy. Therefore, zinc ions (Zn²⁺) occupy interstitial sites, creating a metal excess defect due to anionic (oxygen) vacancies.
• NaCl: Sodium chloride (NaCl) typically exhibits Schottky defects, not metal excess defects due to anionic vacancies.
• FeO: Iron(II) oxide (FeO) primarily demonstrates non-stoichiometry due to metal deficiencies rather than excesses.
• CdO: Like ZnO, cadmium oxide (CdO) can also exhibit metal excess defects due to anionic vacancies, but it is less common compared to ZnO.

Thus, ZnO is the compound that shows metal excess defect due to anionic vacancy.

Question: What is dry ice?

Dry ice is a form of carbon dioxide in its solid state. When carbon dioxide gas is cooled at high pressure, it solidifies to form dry ice. It is commonly used as a cooling agent because it sublimates at -78.5°C (-109.3°F), transitioning directly from a solid to a gas without becoming liquid, which is why it is called "dry" ice. This property makes it ideal for use in situations where a dry cooling environment is needed.

Correct Answer: Solid carbon dioxide

Solution:

The term supercooled liquid refers to a state of matter that retains liquid properties even below its freezing point, where it normally should form a crystalline structure. A classic example of such a material is glass.

Glass is an amorphous solid, meaning it lacks the long-range order characteristic of crystalline structures. Unlike most solids that crystallize upon cooling, glass transitions into a rigid form without forming a crystal lattice. This behavior is why glass is often referred to as a supercooled liquid. The molecules in glass are neither completely free to move as in a true liquid nor are they arranged in a periodic structure like in a crystalline solid. Instead, they are locked into a disordered, glassy state.

Let's examine each option:

• Diamond: A crystalline form of carbon with a highly ordered structure.
• Graphite: Another crystalline allotrope of carbon with layers of hexagonal planes.
• Copper: A metal that forms a crystalline lattice in solid form.
• Glass: An amorphous solid that behaves as a supercooled liquid.

Correct Answer: Glass

For a face-centered cubic (fcc) lattice, the relationship between the edge length (a) and the atomic radius (r) is given by:

Where:

• r = atomic radius
• a = edge length

Given that the edge length (a) is 361 pm, we can calculate the radius (r):

pm

pm

pm

pm

Therefore, the radius of the Cu atom is approximately pm.

The correct answer is (A}: pm