Question

  Give reasons why:                                                                                                                                  
(i)    Unlike many other metals, Cu does not liberate hydrogen gas from dilute acids

(ii)   Metals like Na and K are always kept under kerosene, but gold is kept open.

(iii) Element silver is malleable and ductile, but not sulphur.

(iv)   Diamond is made of C, but very tough  in nature.​

Answer 1

Answer:

1.Copper placed below hydrogen in the electrochemical series. It is not in a position to release electrons to H+ ions of the acid. Therefore, hydrogen gas is not evolved

2.Sodium metal is kept immersed in kerosene oil to prevent accidental fire.

It is very reactive metal and combines explosively with air as well as water. It will catch fire if kept in open.  

Note: Potassium is also  kept immersed in kerosene oil for same reason.

4.Carbon is an extremely versatile element: it has hundreds of hypothetical forms and several observed varieties, including diamond and graphite. In diamond, every carbon atom connects to four others in a 3D cubic lattice that is strong and hard. But in graphite, each atom bonds only to three others, forming flat sheets of hexagons.

hope it helps you