Q1: Boiling temperature of carbon dioxide at atmospheric pressure is __________ °C.

ANS:B - -78.5

The boiling temperature of carbon dioxide at atmospheric pressure, which is approximately -78.5°C, is a critical characteristic of this compound. Let's delve into why this temperature is significant and how it relates to the properties and applications of carbon dioxide:

1. Phase Transition: At atmospheric pressure, carbon dioxide exists as a gas at temperatures above -78.5°C and as a liquid at temperatures below this value. This temperature represents the point at which carbon dioxide undergoes a phase transition from a gas to a liquid. When carbon dioxide is cooled below -78.5°C, its kinetic energy decreases, causing the molecules to condense and form a liquid.
2. Storage and Transportation: The low boiling temperature of carbon dioxide makes it feasible to store and transport it in its liquid form under moderate pressure. Liquid carbon dioxide occupies significantly less volume compared to gaseous carbon dioxide, allowing for more efficient storage and transportation in containers such as cylinders and tanks. This property is crucial for various industries that utilize carbon dioxide, including food and beverage, pharmaceuticals, and manufacturing.
3. Carbonation: In the food and beverage industry, carbon dioxide is widely used for carbonation, giving carbonated beverages their characteristic fizz and effervescence. By adding pressurized liquid carbon dioxide to beverages, such as soda and sparkling water, carbon dioxide gas is released upon opening the container, creating bubbles that enhance the sensory experience of the drink.
4. Refrigeration: Carbon dioxide also serves as a refrigerant in certain applications, particularly in industrial and commercial refrigeration systems. By utilizing the phase transition between liquid and gas at -78.5°C, carbon dioxide can absorb heat energy from its surroundings during vaporization (boiling) and release heat energy during condensation. This property makes it suitable for cooling and refrigeration purposes, particularly in environmentally friendly refrigeration systems.
5. Dry Ice Production: When carbon dioxide gas is compressed and cooled to below its triple point (-56.6°C), it directly solidifies into a solid form known as dry ice without passing through the liquid phase. Dry ice is commonly used for various applications, including cooling, preservation, and special effects, due to its sublimation properties.