Question

One mole is equal to number of atoms as contained in:
A. 1g of carbon
B. 6g of carbon
C. 12g of carbon
D. 12kg of carbon

Answer 1

A substance's molar mass is the mass in grams of one mole of that substance. The molar mass of an element is the mass of one mol of the element's atoms; for a covalent molecular compound, it is the mass of one mol of the compound's molecules; and for an ionic compound, it is the mass of one mol of formula units.

Complete answer:
That is, a substance's molar mass is the mass (in grams per mole) of the substance's $6.022 \times 10^{23}$ atoms, molecules, or formula units. In each case, the numbers of atomic mass units that describe the atomic mass, molecular mass, or formula mass are the same as the number of grams in 1 mol. The mass of a sample of a chemical compound divided by the volume of material in that sample, measured in moles, is the molar mass of that compound.
The mass of one mole of isotopically pure carbon-12 is 12 g. That is, one mole equals the number of atoms in 12 grams of carbon.
Hence the correct answer is option C.

Note:
Remember that the number of atoms in precisely 12 grams of pure carbon-12 is equal to the mole's weight. Also we should note that the mass of 1 mol of atoms of an element is the molar mass. An element’s molar mass in $gmo{l^{ - 1}}$ is numerically equal to the element’s atomic mass in amu.