Question

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 the solid-state whereas it does conduct electricity in aqueous solution as well as in the molten state 

(d) Iron articles are galvanized. 

(e) Metals like Na, K, Ca and Mg are never found in their free state in nature

Answer 1

(a) 

• Reactivity of Aluminium decreases if it is dipped in HNO₃ because HNO₃ is a strong oxidizing agent. 
• Here a layer a layer of aluminium oxide gets deposited because of which reactivity of alumnium gets reduced . 

(b) 

• Carbon cannot reduce the oxides of Na or Mg because these are highly reactive metals. 
• Na and Mg have higher affinity to oxygen than carbon. 
• Hence carbon fails to reduce the oxides of Na and 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 because NaCl is an ionic compound.
• Ionic compounds cannot conduct electricity in solid state but they can conduct electricity in aqueous solution and in molten state

(d) 

• Iron readily reacts with atmospheric oxygen and forms rust.
• To avoid rusting of iron it is galvanized. 

(e)

• Metals like Na, K, Ca and Mg are are highly reactive metals. 
• They can form compounds with almost every element . 
• Because of this they are not found in their native form in nature.