Give reasons: (i) "Alloys of iron are more useful when compared to pure iron."
(ii) Copper loses its brown layer gradually when exposed to air.
(iii) Aluminium oxide is called amphoteric oxide.

Give reason : (i) "Alloys of iron are more useful when compared to pure iron" (ii) Alumunium oxide is called amphoteric oxide

Write the balanced chemical equations for the following reactions : (i) When copper is heated in air. (ii) When aluminium oxide reacts with sodium hydroxide.

Give reasons : i) lonic compounds in solid state do not conduet electricity, whereas in molten state are good conductors of electricity. (ii) ii) Silver articles when exposed to air gradually turn blackish. ii) Chenmical reaction does not take place when copper is added to iron sulphate solution.

Write balanced equations for the reactions of : (i) Aluminium when heated in air. Write the name of the product. (ii) Iron with steam. Name the product obtained. (iii) Calcium with water. Why does calcium start floating in water ?

State reason for the following : (i) Non-metals cannot displace hydrogen from the acids. (ii) Hydrogen is not a metal, yet it is placed in the activity series of metals. (iii) Aluminium is more reactive than iron, yet its corrosion is less than that of iron.

Give reason : (i) Ionic compounds in solid state do not conduct electricity, whereas in molten state are good conductors of electricity. (ii) Silver articles when exposed to air gradually turn blackish. (iii) Chemical reaction does not take place when copper is added to iron sulphate solution.