ANS:B - pure gas

A "pure gas" refers to a gas that consists of only one type of molecule. In other words, it is a gas composed of molecules of a single chemical compound. Pure gases are often used in various industrial processes, scientific experiments, and everyday applications. Characteristics of pure gases include:

1. Homogeneity: Since pure gases consist of only one type of molecule, they are chemically homogeneous throughout. Each molecule within the gas phase is identical.
2. Uniform Properties: Pure gases exhibit uniform physical and chemical properties under a given set of conditions, such as pressure and temperature. This uniformity simplifies the study and manipulation of these gases.
3. Defined Chemical Composition: The chemical composition of a pure gas is well-defined, making it easier to predict its behavior and interactions with other substances.
4. Ideal Gas Behavior: In many cases, pure gases behave according to the principles of ideal gas behavior, meaning they follow the ideal gas law equation PV = nRT, where P is pressure, V is volume, n is the number of moles of gas, R is the ideal gas constant, and T is temperature (in Kelvin). However, real gases may deviate from ideal behavior under certain conditions.

Examples of pure gases include oxygen (O2), nitrogen (N2), hydrogen (H2), carbon dioxide (CO2), and helium (He). These gases are often used in their pure form for various applications, such as in industrial processes, medical treatments, food packaging, and scientific research.