The mass of 14.25 times 10 to the twenty-fifth power of an inert gas molecule is 5kg. What kind of gas is it?

To determine a gas, we need to find its molar mass.
Let’s write an expression to determine the amount of a substance:
ν = m / M = N / Na, where m is the mass of the substance, M is the molar mass of the substance, N is the number of particles, Na is Avogadro’s constant Na = 6.023 * 10 ^ 23 1 / mol.
Let us express M from this expression:
M = m * Na / N
Substitute the numerical values:
M = m * Na / N = (5 * 6.03 * 10 ^ 23) / (14.25 * 10 ^ 25)) = 0.021 kg / mol.
According to the periodic table, we look at which substance has a molar mass of 0.021 kg / mol, in the table it is indicated in g / mol, we are looking for 21 g / mol, we find that it is Neon.
Answer: molar mass 0.021 kg / mol, this is Neon.