What is corrosion? What are the factors which affect corrosion? f

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251. Define conductivity and molar conductivity for the solution of an electrolyte.
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252.

On the basis of the standard electrode potential values stated for acid solution. Predict whether Ti4+ species may be used to oxidise FeII to FeIII.
Reaction: E°/V TiIV + e → Ti3+ + 0.01
Fe3+ + e → Fe2+ + 0.77

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253. What are fuel cells? Write the electrode reactions of a fuel cell which uses the reaction of hydrogen with oxygen.
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254.

Predict the products of electrolysis obtained at the electrodes in each case when the electrodes used are of platinum.
(i) An aqueous solution of AgNO3.
(ii) An aqueous solution of H2SO4.

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255. Define the following terms: (i) Cathodic protection, (ii) Electrochemical series, (iii) Cell constant, (iv) Equivalent conductivity, (v) Strong and weak electrolytes.
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256. Explain the working of galvanic cell. How does the electrochemical cell differ from electrolytic cell?
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 Multiple Choice QuestionsShort Answer Type

257. What is normal hydrogen electrode? Discuss its uses.
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 Multiple Choice QuestionsLong Answer Type

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258. What is corrosion? What are the factors which affect corrosion?


Corrosion is the process of slowly eating away of the metal due to attack of the atmospheric gases on the surface of the metal resulting into the formation of compounds such as oxides, sulphides, carbonates, etc. 
The rusting of iron, tarnishing of  silver, development of green coating on copper and bronze are some of the examples of corrosion.

The main factors which affect corrosion are

Presence of water and the electrolytes present in it.
1.   More the reactivity of metal, the more will be the possibility of the metal getting corroded.

2.   The impurities help in setting up voltaic cells, which increase the speed of corrosion

3.   Presence of electrolytes in water also increases the rate of corrosion

4.   Presence of CO2 in natural water increase rusting of iron.

5.   When the iron surface is coated with layers of metals more active than iron, then the rate of corrosion is retarded.

6.   A rise in temperature (with in a reasonable limit) increases the rate of corrosion.

 

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259. Distinguish between: (a) Electrolytes and non-electrolytes, (b) Reduction potential and oxidation potential (c) Primary cells and secondary cells, (d) Specific conductivity and molar conductivity.
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260.

The conductivity of 0.01 M solution of acetic acid at 25°C is 1.63 x 10–4 s cm–1. Given:
Λ°m (HCl) = 426 s cm2 mol–1, Δ°m (Na AC) = 91.5 cm2 mol–1
Λ°m (NaCl) = 126.5 cm2 mol–1 Calculate:
(a) the molar conductivity of acetic acid
(b) the degree of dissociation of acetic acid.
(c) the dissociation constant.
 (d) the pH of 0.01 M solution of acetic acid.

 
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