Explain the following
(a) Reactivity of Al decreases if it is dipped in HNO3
(b) Carbon cannot reduce the oxides of Na or Mg
(c) NaCl is not a conductor of electricity in solid state whereas it
does conduct electricity in aqueous solution as well as in
molten state
(d) Iron articles are galvanised.
(e) Metals like Na, K, Ca and Mg are never found in their free state
in nature
Answers
Answer:
(a)When Al is dipped in nitric acid a layer of aluminium oxide is formed on the metal. This happens because nitric acid is a strong oxidizing agent. The layer of aluminium oxide prevents further reaction of aluminium and due to this reactivity of Al decreases.
(b)Now, the reactivity series clearly explains that carbon cannot reduce the sodium, and magnesium due to their highly reactive nature. - Thus, Na, and Mg represents higher affinity towards the oxygen because oxygen is highly reactive and it can easily reduce these metals.
(c)In solid NaCl, the movement of ions is not possible due to its rigid structure but in aqueous solution or molten state, the ions can move freely. These free ions are responsible for conduction of electricity.
(d)Iron articles are galvanized to prevent rusting of iron. After galvanization,the layer of zinc works as protective layer.It is the process of applying a protective zinc coat to iron to prevent rusting
(e)Metals like Na, Ca and Mg are very reactive metals, they react with oxygen even at room temperature therefore they are never found in free state in nature.
Answer:
(a) Nitric acid is a strong oxidizing agent. Due to this, when aluminium is dipped in nitric acid, a layer of aluminium oxide is deposited on aluminium. As a result; reactivity of aluminium decreases when it is dipped in nitric acid.
(b) Sodium and magnesium are highly reactive metals. Hence, they have higher affinity to oxygen than to carbon. Due to this, carbon fails to reduce the oxides of sodium or magnesium.
(c) NaCl is an ionic compound. Ionic compounds do not conduct electricity in solid state. But ionic compounds are good conductors of electricity in molten state and in aqueous solution.
(d) Iron has a tendency to react with atmospheric moisture. This process is called rusting and leads to corrosion of iron. Iron articles are galvanized to prevent rusting of iron.
(e) Na, K. Ca and Mg are highly reactive metals. They can easily form compound with most of the elements. Due to this, these metals are not found in their free state in nature.