16.0 grams of molecular oxygen gas is equal to

One thing to notice in the question is, we are asked about molecular oxygen that has formula O2 not atomic oxygen O.

As we are asked about molecular oxygen, we will answer the question in terms of number of molecules that are present in 16 grams of molecular oxygen.

To get the number of molecules present in 16 grams of O2, we will use the formula:

         No. of molecules = no. of moles x Avogadro's number (NA)  eq 1)

As we know:

                        The number of moles = mass/ molar mass of molecule

Here we have been given mass already, 16 grams and the molar mass of O2 is 32 grams.

Putting the values in above formula:

                                                    = 16/32  

                                                     = 0.5 moles

Putting the number of moles and Avogadro's number (6.02 * 10^23) in eq 1

                                No. of molecules = 0.5  x 6.02 * 10^23

                                   =3.01 x 10^23 molecules

or                 301,000,000,000,000,000,000,000 molecules

This means that 16 grams of 3.01 x 10^23 molecules of oxygen.

Hope it helps!

the answer is c. nacl