Question

Write balanced chemical equations to explain what happens, when
(1) Mercuric oxide is heated.
6) Mixture of cuprous oxide and cuprous sulphide is heated.
(u) Aluminium is reacted with manganese dioxide.
(iv) Ferric oxide is reduced with aluminium.
(y) Zinc carbonate undergoes calcination.​

Answer 1

Explanation:

Mercury(II) oxide, a red solid, decomposes when heated to produce mercury and oxygen gas. A reaction is also considered to be a decomposition reaction even when one or more of the products are still compounds. A metal carbonate decomposes into a metal oxide and carbon dioxide gas.

Answer 2

The balanced chemical equations are:

(1)2HgO + Heat → 2Hg + O₂

(6) 2Cu₂O + Cu₂S → 6Cu + SO₂

(u) 4Al + 3MnO₂ → 2Al₂O₃ + 3Mn

(iv) 2Al + Fe₂O₃ → Al₂O₃ + 2Fe

(v)ZnCO₃ +Heat → ZnO + CO₂

(1) When mercuric oxide (HgO), a red solid, is heated at very high temperature, it decomposes to give mercury (Hg), a grey residue and Oxygen gas (O₂) liberates.

2HgO + Heat → 2Hg + O₂

(6) When cuprous oxide (Cu₂O) and cuprous sulphide (Cu₂S) is heated, we get copper metal as residue along with the evolution of SO₂ gas.

2Cu₂O + Cu₂S → 6Cu + SO₂

(u) When Aluminium (Al) is reacted with manganese dioxide (MnO₂), we get Aluminium oxide (Al₂O₃) and Manganese (Mn) as residue.\

(iv) When ferric oxide (Fe₂O₃) is reacted with aluminium (Al), we get Aluminium oxide (Al₂O₃) and iron (Fe) as residue.

2Al + Fe₂O₃ → Al₂O₃ + 2Fe

(y) When zinc carbonate (ZnCO₃) is calcinated (heated in the absence of air), zinc oxide, ZnO (yellow when hot and white when cold) is formed as residue along with the evolution of CO₂ gas.

ZnCO₃ +Heat → ZnO + CO₂