The density of air at STP is 1.285 g/L. Which of the following cannot be used to fill a balloon that will float in air at STP?

NO can't  be used to fill a balloon

Conditions at T 0 ° C and P 1 atm are stated by STP (Standard Temperature and Pressure). At STP, Vm is 22.4 liters/mol.

Answer options that need to be added :

a. Ne

b. NO

c. NH₃

d. CH₄

e. HF

will float in air ⇒ element or compound to fill the balloon, its density must be less than < 1.285 g/L

We can use the ideal gas formula ta find density :

Because at STP, then the constant value is

So that the density is determined from the MW(molecular weight) of each element or compound

Ar = 20.1797 g/mol

MW=30.006 g/mol

MW=17.0306 g/mol

MW=16.04 g/mol

MW=20.01 g/mol

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)