Calculating the number of neutrons in a sample Which of the following contains one mole of neutrons?
A. $\pu{1 g}$ of $\ce{^1_1H}$
B. $\pu{1 g}$ of $\ce{^{12}_6C}$
C. $\pu{2 g}$ of $\ce{^{24}_{12}Mg}$
D. $\pu{2 g}$ of $\ce{^{23}_{10}Ne}$

Here's a question which I don't know how to answer. I tried using the equation:
moles=mass/mr
but that did not match the answer given, which is (C). I keep doing 2/24 which doesn't appear to equal 1 mole.
The formula

$$\text{amount of substance} = \frac{\text{mass}}{\text{molar mass}}$$

tells you that you have 1/12 moles of magnesium, since you are taking the mass of magnesium (2 g) and dividing by the molecular mass of magnesium (24 g/mol). However, the question is not asking about the number of moles of magnesium.

Each magnesium atom has 24 - 12 = 12 neutrons. Consequently, 1/12 moles of magnesium has (1/12)(12) = 1 mole of neutrons.