Question

Give reasons:
a)The surface of the article to be electroplated should be free from non-metallic impurities.
b) A low current and for a longer time should be used during electroplating.
c) A direct current and not an a.c current should be used during electroplating.
d) The metal anode has to be replaced periodically during electroplating.
e) Silver nitrate is not preferred as an electrolyte during electroplating of an iron spoon with silver.
f) The article to be plated is always placed at the cathode.

Answer 1

$$\begin{gathered} a\text{. The surface of the article to be electroplated should be free from non-metallic impurities} \\ \text{Reason : Non metallic impurities cause discontinuous coating and make the surface rough.} \\ b.\text{A low current and for a longer time should be used during electroplating} \\ \text{Reason : Low current for a longer time cause a smooth, uniform and long lasting deposition of material.} \\ \text{High current causes irregular deposition of the metal.} \\ \text{c. A direct current and not an a.c current should be used during electroplating} \\ \text{Reason: No ionisation and discharge at the cathode occur thereby giving effective coating.} \\ \text{d. The metal anode has to be replaced periodically during electroplating.} \\ \text{Reason : The anode metal continuously dissolves and should be replacd periodica}lly. \\ e.Silvernitrate \\ \mathrm{Reason:\; As\; iron\; is\; more\; reactive\; than\; silver\; it\; displaces\; silver\; from\; silvernitrate\; solution\; thereby\; the\; spoon\; dissolves.} \\ \mathrm{f.\; The\; article\; to\; be\; plated\; is\; always\; placed\; at\; the\; cathode} \\ \mathrm{Reason}\text{: Metal is depoisted at the cathode by reduction process, i.e., by gain of electrons.} \\ A \end{gathered}$$