Question

what is the key factor to use in converting between mass and moles?
a. atomic number
b. molar mass
c. volume
d. density

Explanation:

Molar mass ($M$) is defined as the mass ($m$) per mole ($n$) of a substance, with the formula $M=\frac{m}{n}$. So, it directly relates mass and moles. Atomic number relates to the number of protons in an atom. Volume and density are related to mass ($m =
ho V$, where $
ho$ is density and $V$ is volume) but not directly to moles in the way molar mass is.

Answer:

B. Molar mass