3pr 2nd Sci U1L1:Chemical Reactions

In the thermal decomposition reactions, the compound decomposes by heat into its …........

• simple components.
• primary elements.
• other compounds.
• all the previous answers.

When we heat mercuric oxide, we get …...............

• mercuric oxide and water.
• mercuric oxide and oxygen.
• mercury and hydrogen.
• mercury and oxygen.

When copper hydroxide is heated, we obtain …........

• copper carbonate and water.
• copper oxide and water.
• copper oxide and hydrogen.
• copper and hydrogen.

When calcium carbonate is heated, ….......... are obtained.

• calcium bicarbonate and carbon dioxide
• calcium hydroxide and carbon dioxide
• calcium oxide and carbon monoxide
• calcium oxide and carbon dioxide

On heating copper carbonate, the colour changes from …................

• blue to black.
• green to black.
• black to green.
• green to blue.

Most metal sulphates decompose when they are heated to metal oxide and …... gas.

• CO₂

• O₂

• SO₂

• SO₃

On heating copper sulphate, a …........ colour is formed.

• black
• green
• blue
• red

Copper sulphate is decomposed by heat into…...........

• black copper oxide only.
• sulphur trioxide gas only.
• sulphur dioxide gas and black copper oxide.
• black copper oxide and sulphur trioxide gas.

Some metal nitrates are decomposed by heat into …..............

• metal nitrite and oxygen gas.
• metal nitrate and oxygen gas.
• nitrogen oxide and oxygen gas.
• metal nitrate and water.

The oxygen (O₂) evolves by heating …............. compound.

• NaNO₃

• CuSO₄

• CuCO₃

• Cu(OH)₂