1. Which of these chemical formulasCl2, KCl, Ar, or NO2represents both an element and a molecule?

Question

2. A miner finds a small mineral fragment with a volume of 5.74 cm3 and a mass of 14.4 g. What is the density of that mineral fragment?

Answer 1

Ar is an element. It also is a molecule.
From the way the question is worded, I'm tempted to pick Cl2 also; however, Cl is the element and Cl2 is the molecule. For that reason I'm not including it.

#2. density = mass/volume.