IIT-JEE-Chemistry-Final Revision Set No.89

1. STATEMENT-1 : There is a natural asymmetry between converting work to heat and converting heat to work.

and

STATEMENT-2 : No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work.

(A) Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for statement-1.

(B) Statement-1 is True, Statement-2 is True, Statement-2 is not a correct explanation for statement-1.

(C) Statement-1 is True, Statement-2 is False

(D) Statement-1 is False, Statement-2 is True


Paragraph BASED QUESTIONS

In hexagonal systems of crystals, a frequently encountered arrangement of atoms is described as a hexagonal prism. Here, the top and bottom of the cell are regular hexagons and three atoms are sandwiched in between them. A space-filling model of this structure, called hexagonal close-packed (HCP), is constituted of a sphere on a flat surface surrounded in the same plane by six identical spheres as closely as possible. Three spheres are then placed over the first layer so that they touch each other and represent the second layer. Each one of these three spheres touches three spheres of the bottom layer. Finally, the second layer is covered with a third layer that is identical to the bottom layer in relative position. Assume radius of every sphere to be 'r'.

2. The number of atoms in this HCP unit cell is

(A) 4

(B) 6

(C) 12

(D) 17

3. The volume of this HCP unit cell is

(A) 24 √2 r³

(B) 16 √2 r³

(C) 12 √2 r³

(D) 64/3√3 r³

4. The empty space in this HCP unit cell is

(A) 74%

(B) 47.6%

(C) 32%

(D) 26%

5. Identify the process used to extract the metal/compound from the given ore

Roasting, Calcinations, Carbon reduction, Self reduction


PbS --> PbO

CaCO3 --> CaO

ZnS --> Zn

Cu2S --> Cu


Source: IIT JEE 2008 paper 2