Answer:
Judging from the wording of he question, you mean units. If that is indeed the case, the answer is g/Mol (grams per mol)
Let me know if my interpretation is incorrect and please tell me what you are actually trying to find.
The compound is Al2O3. The ratio of aluminum to oxygen is 2:3.
The relative mass of each element can be found from the periodic table (the larger number). For instance, P2O5, P = 31.0 O = 16.0, thus the formula mass (Mr) is 2(31) + 5(16) = 142 amu (atomic mass unit). I used a not really specific periodic table. Maybe your teacher is referring to open Schoology (a website where teacher can post files or announcements to students in his or her class). Sorry if i got something mistaken.
Answer:
4.20 moles NF₃
Explanation:
To convert between moles of N₂ and NF₃, you need to use the mole-to-mole ratio from the balanced equation. This ratio consists of the coefficients of both molecules from the balanced equation. The molecule you are converting from (N₂) should be in the denominator of the ratio because this allows for the cancellation of units. The final answer should have 3 sig figs because the given value (2.10 moles) has 3 sig figs.
1 N₂ + 3 F₂ ---> 2 NF₃
2.10 moles N₂ 2 moles NF₃
--------------------- x --------------------- = 4.20 moles NF₃
1 mole N₂
is 
, hence one 
is 
, thus 
is 
