chem question

briefly describe the variious methods of rust prevention and the underlying principles of each method (6 marks)
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A. apply a protective layer. to avoid the metal direct contact with oxygen and water.
e.g. coating with paint , plastic, oil or grease.
coating with another metal
electroplating

B. cathodic protceiton
the negative terminal of a car battery is always connected to the car body. supplies electrons to the iron body, preventing it from losing electrons.

C. sacrificial proteciton
connect iron to a more reactive metal. that metal will lose electrons in preference to iron. prevent Fe(S) from forming Fe2+ ions

D.using alloys of iron.
to fight against corrosion, steel can be alloyed with other metal e.g.nickel to produce stainless steel.

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1M nitric acid is a dilute solution of a strong acid,but10M ethanoic acid is a concentrated solution of a weak acid.Explain the above statement and put down related equations
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HNO3 + water -------(complete ionization) -----> H+ (aq) + NO3- (aq)
CH3COOH +water ----------(slight ionization)-----> CH3COO-(aq) + H+(aq)
the strength of acids and alkalis is refer to their extent of ionization or dissociation in aqueous solution.
HNO3 is strong acid because it is completely ionize in water.
CH3COOH is weak because it is ionizes only slightly in water.

concentration refer to the amount of solute per unit volunme of solution.
that mean CH3COOH have more solute in the solution and so it is concentrated.