How many atoms do mercury vapour molecules consist of if the density of mercury vapour relative to air is 6.92?(Hg=200).The average mass of aiir is 29g/mole.

To determine how many atoms are in mercury vapor molecules, we first need to understand the relationship between the density of the vapor, its molecular weight, and the molecular composition of mercury itself. Let's break this down step by step.

Understanding Density and Molecular Weight

The density of a gas can be expressed in terms of its molecular weight and the density of air. The formula for the density of a gas is given by:

Density = (Molecular Weight / Molar Volume)

In this case, we know that the density of mercury vapor relative to air is 6.92. The average molar mass of air is approximately 29 g/mol. Therefore, we can calculate the molecular weight of mercury vapor using the following relationship:

Calculating the Molecular Weight of Mercury Vapor

Since the density of mercury vapor is 6.92 times that of air, we can express the molecular weight of mercury vapor as:

Molecular Weight of Hg Vapor = 6.92 × Molar Mass of Air

Substituting the values:

Molecular Weight of Hg Vapor = 6.92 × 29 g/mol = 200.68 g/mol

This value is very close to the atomic mass of mercury (Hg), which is approximately 200 g/mol. This suggests that mercury vapor primarily consists of diatomic molecules (Hg₂) rather than monatomic mercury (Hg).

Determining the Composition of Mercury Vapor

Mercury, in its gaseous form, typically exists as diatomic molecules (Hg₂). This means that each molecule of mercury vapor consists of two mercury atoms. Therefore, if we consider the molecular weight we calculated, it aligns with the idea that the vapor consists of pairs of mercury atoms.

Conclusion on Atomic Composition

To summarize, since mercury vapor primarily exists as diatomic molecules, each molecule consists of:

• 2 atoms of mercury

Thus, the answer to your question is that mercury vapor molecules consist of 2 atoms. This understanding is crucial in fields such as chemistry and environmental science, where the behavior of gases and their molecular compositions play significant roles in various applications.