Which of the following is an empirical formula?

Question

NaO
C2H8N2
C6H3Cl2

What is the percent carbon in carbon dioxide?

12.01%
27.3%
44.009%

What is the percent nitrogen in potassium nitrate?

13.9%
101.1%
19.007%

Answer 1

NaO. The others are molecular formulas whose subscripts are not reduced to the lowest common denominators.

Atomic weights: C=12 O=16 CO2=44
12gC/44gCO2 x 100% = 27.4%

Atomic weights: K=39 N=14 KNO3=101
14gN/101gKNO3 x 100% = 13.9%