Oxygen was discovered by Joseph Priestley in 1774 when he heated mercury (II) oxide to decompose it to form its constituent elements.

Question

a. How many moles of mercury (II) oxide, HgO, are needed to produce

125 g of oxygen, O₂?

b. How many moles of mercury are produced?

Answer 1

Write the balanced equation:

2HgO ==> 2Hg + O2

a). 125 g O2 x 1 mol O2/32 g x 2 mol HgO / mol O2 = 7.81 moles HgO

b). 125 g O2 x 1 mol O2/32 g x 2 mol Hg / mol O2 = 7.81 moles Hg