Question

What is the molar mass of a gas whose density at stp is 3.74 g/l?

Answer 1

p = 3,74 g/l
p = M / 22,4 l
M = p × 22,4l

M = 3,74 g/l × 22,4l = 83,776 g

The molar mass of this gas is 83,776 g.

:-) ;-)