C). How many mole of oxygen would be produced from reacting 7 mole of HgO (mercury (II) oxide) ?

There will be produced 3.5 moles of oxygen (O2)

Explanation:

Step 1: Data given

Number of moles Mercury (II) oxide (HgO) = 7 moles

Step 2: The balanced equation

2HgO → O2 + 2Hg

Step 3: Calculate number of moles of O2

For 2 moles of Mercury (II) oxide (HgO) we produce 1 mol of O2 and 2 moles of Hg

For 7 moles of Mercury (II) oxide (HgO) we'll have 7/2 = 3.5 moles of O2

There will be produced 3.5 moles of oxygen (O2)