Chapter 6 Chem XII

Question6.1: Why damage tin plated cause should be avoided?

Answer: When iron sheet is coated with tin metal, it does not corrode. But when tin coating is damaged then Galvanic cell is developed between tin and iron. Tin acts as cathode and iron acts as anode. Therefore electron flow from iron to tin. As a result, H+, OH-, and Fe+3 ions are produced solution. Hence Fe forms Fe(OH)3, and corrod. Result is that after damage templating the collision of iron takes place more rapidly.

Question 6.2: Under what conditions aluminium crrods?

Answer: When Aluminium is brought in contact with copper it slows corrosion. As a result, a galvanic cell is formed between aluminium and copper. The aluminium acts as an anode and copper acts as cathode. Thus aluminium loses electron and forms Al3+ ions. The electron move from aluminium to Copper to forma Al(OH) 3 which starts to dissolve. In this way Aluminium is eaten away and shows Korean but copper image in tact.

Question 6.3: How does the process of galvanizing protect iron from rusting?

Answer: The process in which a thin layer of zinc is coated on iron sheet is called galvanising or zinc coating. Zinc coating is done by dipping a clean sheet of iron first in zinc chloride bath and then in zinc-bath. When zinc coating is damaged then Galvanic cell is established between zinc and iron. and electron flow from zinc to iron and thus zinc is eaten a decayed away but iron remains understand. it is called sacrificial Corris ion.

Fe2+ zinc --> Zn2+ Fe

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