***20 pts*** If you had 3.02 grams of Sodium (Na), how many moles would that be?
ANSWER W STEPS IF NOT REPORTED

0.131 mol

Explanation:

To convert grams to moles, you need to use the molar mass.  The molar mass is the mass number.  You can find this on the periodic table.  The molar mass of sodium is 22.990 g/mol.

(3.02 g)/(22.990 g/mol) = 0.131 mol

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.