Metals and Non-metals - 2 (Class X)

Its constituents are iron and carbon.

It is non-reactive with dilute HCl but reacts with H₂SO₄.

The refining of a metal (such as copper) by electrolysis, in which the crude metal used as the anode goes into solution and the pure metal is deposited upon the cathode is called electrolytic refining.

Sodium reacts vigorously with cold water displacing hydrogen.

Zone melting (or zone refining or floating zone process) is a group of similar methods of purifying crystals, in which a narrow region of a crystal is molten, and this molten zone is moved along the crystal (in practice, the crystal is pulled through the heater). The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot. The impurities concentrate in the melt, and are moved to one end of the ingot.

 Barrier protection is the oldest and most widely used method of corrosion protection. It acts by isolating the base metal from the environment. Like paints, the hot-dip galvanized coating provides barrier protection. A barrier film is introduced between iron and atmospheric oxygen and moisture.

This process is used for refining easily fusible metals like lead and tin. The impure metal is heated on the sloppy hearth of an electric furnace. The metal melts and flows down, leaving the impurities.

Calcium is the most reactive according to the reactivity series (activity series) of metals.
Decreasing chemical reactivity is:
K > Na > Ca > Mg > Al > Zn > Fe > Sn > Pb > H > Cu > Hg > Ag > Au

The corrosion will be enhanced:
(a)  if impurities are present in the metal
(b)  in the presence of carbon dioxide
(c)  if the metal is highly reactive  

Iron is shiny grey but it reacts with water vapours and oxygen present in air. After the reaction, its surface gets covered with the coating of a brown flaky substance called rust. Rust is mainly hydrated ferric oxide (Fe₂O₃.xH₂O). Both gold and silver are unreactive in nature.

Nickel and steel are ferrous alloys.

 When a metal mixed is with mercury, the alloy formed is known as an amalgam.

This option is correct because electrochemical series does not provide a generalization to the rate of corrosion of elements as per their position in electrochemical series. For example: In Zn-Al couple, zinc is corroded and Al behaves as cathodic part. However, Al is above Zn in electrochemical series, which is due to the fact that Al develops strongly adhering oxide layer on its surface, thereby making effective electrode potential more positive.

The composition of alloy duralumin are Al, Cu, Mg and Mn.

This is the correct option. Copper is the least reactive metal.