1,3,2
The coefficient multiplied by the subscript will give you how many atoms of the element there are.
So, if we plug in 1,3,2
There will be 2 Nitrogen and 6 Hydrogen in the reactants side of the equation. To balance this on the other side, we must put a 2 in order to get 2 Nitrogen and 6 Hydrogen again.
Answer:
The mole fractions:




Explanation:
The reaction described is:

The limiting reactant is the HBr (oxygen is in excess).
a) The mass (in moles) balance for this sistem:
(the 0.78 is because of the fractional conversion)

(the 1.25 is because of the oxygen excess)
There is only one degree of freedom in this sistem, you can either deffine the moles of HBr you have or the moles of Br2 you want to produce. The other variables are all linked by the equations above.
b) Base of calculation 100 mol of HBr:




The mole fractions:




Barium is in group 2A, it looses 2 electrons to form the calcium ion BA2, i’ll send a picture of some of my notes, hopefully it helps:))
I think that it would be 12