In a cubic dosed packed structure of mixed oxides, the lattice is made up of oxide ions, one eighth of tetrahedral/voids are occupied by divalent ions \[({{A}^{2+}}),\] while one half of the octahedral voids are occupied by trivalent ions \[({{B}^{3+}})\]. What is the formula of the oxide?
In fcc lattice, A, B, C, D atoms are arranged at corners, face centres, octahedral voids and tetrahedral voids respectively, then the body diagonal contains
Ferrous oxide has a cubic structure and each edge of the unit cell is \[5.0\text{ }{{A}^{o}}\]. Assuming density of the oxide as \[4.0\text{ }g\text{ }c{{m}^{-3}}\] the number of \[F{{e}^{2+}}\] and \[{{O}^{2-}}\] ions present in each unit cell will be
A metallic element has a cubic lattice. Each edge of the unit cell is \[2{{A}^{0}}\]. The density of the metal is \[2\text{ }g\text{ }c{{m}^{-3}}\]. The unit cells in 200 g of the metal are
DIRECTION: Read the passage given below and answer the questions that follows:
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 sandwiched in between them. A space-of this 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. There 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 third layer that is identical to the bottom layer in relative position. Assume radius of every sphere to be 'r'.
DIRECTION: Read the passage given below and answer the questions that follows:
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 sandwiched in between them. A space-of this 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. There 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 third layer that is identical to the bottom layer in relative position. Assume radius of every sphere to be 'r'.
DIRECTION: Read the passage given below and answer the questions that follows:
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 sandwiched in between them. A space-of this 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. There 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 third layer that is identical to the bottom layer in relative position. Assume radius of every sphere to be 'r'.
Iron crystallizes in several-modifications. At about \[910{}^\circ C\] 'bcc' form (called \[\alpha -\]form) undergoes transitions, to \[\gamma -\]form with 'fcc' lattice. Assuming that the distance between the nearest neighbors is the same in the two forms at the transition temperature, calculate the ratio of the density of \[\gamma -\]ron to that of \[\alpha -\]iron at the transition temperature.
A metal crystallizes into two cubic phases, face centred cubic (fee) and body centred cubic (bcc) whose unit cell lengths are 3.5 and \[3.0\,\overset{o}{\mathop{A}}\,\] respectively. Calculate the ratio of the densities of fee and bee.
A compound formed by elements A and B has a cubic structure in which A atoms are at the comers of the cube and B atoms are at the face centres. The formula for the compound is
When heated above \[916{}^\circ C,\] iron changes its bcc crystalline form to fcc without the change in the radius of atom. The ratio of the density of the crystal before heating and after heating is:
A crystal is made of particles A and B. A forms fcc packing and B occupies all the octahedral voids. If all the particles along the plane as shown in the figure are removed, then the formula of the crystal would be:
List-I and List-II contains four entries each. Entries of List-I are to be matched with some entries of List-II. One or more than one entries of List-I may have the matching with the same entries of List-II.
In hexagonal close packing of sphere in three dimensions, which of the following statements is correct.
A)
In one unit cell there are 12 octahedral voids and all are completely inside the unit cell.
doneclear
B)
In one unit cell there are six octahedral voids and all are completely inside the unit cell.
doneclear
C)
In one unit cell there are six octahedral void and of which three are completely inside the unit cell and other three are partially inside the unit cell.
doneclear
D)
In one unit cell there are 12 tetrahedral voids, all are completely inside the unit cell.
Lithium borohydride crystallizes in an orthorhombic system with 4 molecules per unit cell. The unit cell dimensions are \[a=6.8\text{ }\overset{o}{\mathop{A}}\,,\,b=4.4\overset{o}{\mathop{A}}\,\] and \[c=7.2\overset{o}{\mathop{A.}}\,\] If the molar mass is 21.76, then the density of crystals is: