Problem 11
Among the following unit cells given below, which one has the highest symmetry? (a) cubic (b) monoclinic (c) hexagonal (d) orthorhombic
Problem 12
The total elements of symmetry in a cube are (a) 23 (b) 14 (c) 25 (d) 16
Problem 13
In which of the following crystal systems the endcentred unit cell exists? (a) monoclinic (b) triclinic (c) cubic (d) all of these
Problem 15
The empty space left in a hexagonal close packing of spheres in three dimensions is (a) \(64 \%\) (b) \(26 \%\) (c) \(14 \%\) (d) \(52.4 \%\)
Problem 16
Which one of the following is not a close packed arrangement? (a) \(\mathrm{BCC}\) (b) \(\mathrm{ccp}\) (c) \(\mathrm{hcp}\) (d) all of these
Problem 17
The void formed by closed packed array of spheres located at the alternate corners of each face is (a) octahedral void (b) tetrahedral void (c) triangular void (d) both (a) and (b)
Problem 19
The pattern of successive layers of cep arrangement can be designated as (a) \(\mathrm{AB}, \mathrm{ABC}, \mathrm{AB}, \mathrm{ABC} \ldots\) (b) \(\mathrm{AB}, \mathrm{AB}, \mathrm{AB} \ldots\) (c) \(\mathrm{AB}, \mathrm{BA}, \mathrm{AB}, \mathrm{BA} \ldots\) (d) \(\mathrm{BC}, \mathrm{ABC}, \mathrm{ABC} \ldots\)
Problem 21
In simple cubic crystal the radius ratio should be (a) \(\geq 0.732\) (b) \(\leq 0.732\) (c) \(\leq 0.424\) (d) \(\leq 0.225\)
Problem 22
If \(\mathrm{R}\) is the radius of the sphere in the close packed arrangement and \(\mathrm{r}\) is the radius of the tetrahedral void, then (a) \(\mathrm{R}=0.414 \mathrm{r}\) (b) \(\mathrm{r}=0.224 \mathrm{R}\) (c) \(\mathrm{R}=0.225 \mathrm{r}\) (d) \(\mathrm{r}=0.414 \mathrm{R}\)
Problem 24
Which of the following statements about the \(\mathrm{NaCl}\) crystal is correct? (a) \(\mathrm{Cl}\) ions are present at the corners and \(\mathrm{Na}^{+}\)ions at the body-centre (b) \(\mathrm{Cl}\) ions adopt bec arrangement (c) \(\mathrm{Cl}\) ions are packed following ABC ABC pattern of hexagonal close packing (d) \(\mathrm{Na}^{+}\)ions are at the edge centres only
