A noble gas is found to have a density of 3.74 g/L at STP. The possible identity of this gas is:

Answer 1

In an attempt to identify the gas from in information provided, we'd probably want to determine the molar mass of the gas, and even then, identifying it will just be an educated guess.

If we assume that we have 1 liter of the gas, then we have 3.74 g (as defined by the density). Since we are at STP, 1 mol of any ideal gas occupies 22.4 liters (a good number to memorize). Thus, we can now determine how many moles of gas we have.

1 L x 1 mol / 22.4 L = 0.0446 mols of gas

Now we can determine the molar mass

3.74 g / 0.0446 mols = 83.83 g / mol

A likely candidate would be Krypton (Kr) which has a molar mass of 83.3 g/mol

(NOTE: there are probably many other gases in the universe that have a similar molar mass)