Which noble gas has the smallest density at STP? Explain

Short Answer

Expert verified
Helium (He) has the smallest density at STP among the noble gases because it has the smallest molar mass (4 g/mol), and density is directly proportional to molar mass at STP.

Step by step solution

01

Recall the relationship between density, molar mass, and STP conditions

Density at STP is directly proportional to the molar mass of a gas. This means that a gas with a lower molar mass will have a lower density at STP. Mathematically, this relationship can be expressed as follows: Density (D) = (Molar mass (M) × Pressure (P)) / (Ideal Gas Constant (R) × Temperature (T)) In this exercise, we want to compare the densities of noble gases at STP, meaning that Pressure (P) = 1 atm, and Temperature (T) = 273.15K. Since P, R, and T remain constant, the density is directly proportional to molar mass: D ∝ M.
02

Determine the molar masses of the noble gases

We will now determine the molar masses of the following noble gases: 1. Helium (He) 2. Neon (Ne) 3. Argon (Ar) 4. Krypton (Kr) 5. Xenon (Xe) 6. Radon (Rn) You can find the molar masses by referring to the periodic table. They are as follows: 1. Helium (He) - 4 g/mol 2. Neon (Ne) - 20 g/mol 3. Argon (Ar) - 40 g/mol 4. Krypton (Kr) - 84 g/mol 5. Xenon (Xe) - 131 g/mol 6. Radon (Rn) - 222 g/mol
03

Identify the noble gas with the smallest molar mass

Compare the molar masses of the noble gases from Step 2: - Helium (He) - 4 g/mol - Neon (Ne) - 20 g/mol - Argon (Ar) - 40 g/mol - Krypton (Kr) - 84 g/mol - Xenon (Xe) - 131 g/mol - Radon (Rn) - 222 g/mol From the comparison, we can see that Helium (He) has the smallest molar mass of 4 g/mol.
04

Conclude which noble gas has the smallest density

Since density at STP is directly proportional to molar mass, and Helium (He) has the smallest molar mass among the noble gases, we can conclude that Helium (He) has the smallest density at STP.

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