2. Mercury (II) oxide decomposes into mercury and oxygen gas according to the following

skeletal equation.

2 H90 → 2 Hg + L02

a) How many moles of mercury (II) oxide are needed to produce 125 g of oxygen?

7.8 moles are needed.

Explanation:

Given dа ta:

Mass of oxygen produced = 125 g

Number of moles of mercury oxide needed = ?

Solution:

Chemical equation;

2HgO → 2Hg + O₂

Number of moles of oxygen:

Number of moles = mass / molar mass

Number of moles = 125 g / 32 g/mol

Number of moles = 3.9 mol

Now we will compare the moles of oxygen with mercury oxide.

O₂ : HgO

1 : 2

3.9 : 2*3.9 = 7.8 mol