give reason for the following.
1) copper carbonate on heat gives copper oxide and carbon dioxide.
2)a bright light is seen involved when a strip of magnesium is heated.
3) sulphur when burnt in air evolves a gaseous acidic product.
4) an iron nail kept open in the atmosphere rusts.
5)a piece of magnesium strip is dropped into a beaker containing dilute hydrochloric acid.
Answers
Explanation:
1.Copper carbonate on heating decomposes to Copper oxide and carbon dioxide because copper carbonate is thermally less stable.
2.When magnesium burns, it is actually reacting with oxygen in the air and not with fire. Fire is what we call the heat and light produced when things burn. Magnesium reacts with oxygen to make a compound called magnesium oxide. The bright light results because this reaction produces a lot of heat.
3.Sulphur produces sulphur gas when burnt in air, this acidic product is new and changes the composition of sulphur. Hence, it is a chemical change. Iron rust is a brown flaky powder formed after iron reacts with air, a new product with new properties is formed which are different from iron metal.
4.Rusting is a chemical reaction which takes place when iron is exposed to moist air. It reacts with oxygen and water to form iron oxide. So, the iron nail kept near the gateway of India in Mumbai will rust faster because there the humidity is more.
5.When a piece of magnesium strip is dropped in dilute hydrochloric acid, hydrogen gas is evolved and hence it is a chemical change. as new substances, MgCl2 and H2 with new properties are produced and the reaction is irreversible.