How many moles of carbon are there in 19.2g of carbon? how many atoms of copper are in 11.4 moles of copper? how much mass would 3.15 moles of o2 gas have? how many moles of silver are there in 6.51e24 atoms of silver?

*Necessary Information for the calculations*
Molar mass of carbon                  - 12.011 g/mol
Molar mass of copper                  - 63.546 g/mol
Molar mass of molecular oxygen - 31.998 g/mol
Avogadro's number                      - 6.022 x 10^23 atoms/mol

1. Moles of carbon in 19.2 grams of carbon (C)

To determine the number of moles carbon for a given mass of the substance, the mass of the sample is simply divided by its molar mass. Thus,

            19.2 g C  x      1 mol C           = 1.599 mol C
                                 12.011 g C

2. Atoms of copper in 11.4 moles of copper (Cu)

To determine the number of atoms of a substance for a given number of moles, the latter is simply multiplied by Avogadro's number which represents the number of particles, molecules, or atoms of a any substance in 1 mole. Thus, 

            11.4 mol Cu   x   6.022x10^23 atoms Cu     = 6.865x10^24 atoms Cu
                                                1 mole Cu

3. Mass of 3.15 moles of molecular oxygen (O2)

To determine the mass of a given number of moles of a substance, the former is simply multiplied by the molar mass of the substance. Thus,

            3.15 mol O2   x   31.998 g O2     = 100.794 g O2
                                         1 mole O2

4. Moles of silver in 6.51x10^24 moles of silver (Ag)

To determine the number of moles of a substance for a given number of atoms, the latter is simply divided by Avogadro's number. Thus, 

            6.51x10^24 atoms Ag   x             1 mol Ag                 = 10.810 mol Ag
                                                      6.022x10^23 atoms Cu

The answer is probably c. xylem