Answer:
Option C.
2 Mg (s) + O₂(g) → 2MgO (s)
Explanation:
Two moles of magnesium solid react with one mol of oxygen gas to
form two moles of magnesium-oxide solid
2 Mg (s) + O₂(g) → 2MgO (s)
That's the reaction for the magnessium oxide's formation.
Be careful cause we do not say molecules, they are moles.
The stoichiometry indicates the number of moles that react and the moles which are produced.
It is a redox reaction, because the magnessium is oxidized and the oxygen is reduced. Both elements, changed the oxidation states.
Physical......................................................
Answer : The concentration of 
is, 0.12 M
Explanation :
Using Henry's law :
where,
= concentration of = ?
= partial pressure of = 4.5 atm
= Henry's law constant = 
Now put all the given values in the above formula, we get:
Thus, the concentration of is, 0.12 M
Nitrogen. air consists 78% of nitrogen gas
