$CCP$ lattice of a solid made up of $B^{-}$ ions has an edge length of $3 \ \mathring{A}$ and a density of $5 \ g/cm^3$. If in this lattice $A^{+}$ ions are placed at alternate tetrahedral voids,then the percentage increase in density will be $............. \ \%$. [Molar mass of $A^{+} = 30 \ g/mol$,$N_A = 6 \times 10^{23}$]

Which of the following is incorrectly matched?

Give the correct order of initials $T$ (true) or $F$ (false) for the following statements:
$I.$ In an anti-fluorite structure,anions form $FCC$ lattice and cations occupy all tetrahedral voids.
$II.$ If the radius of cations and anions are $0.2 \ \mathring{A}$ and $0.95 \ \mathring{A}$,then the coordination number of the cation in the crystal is $4$.
$III.$ An atom/ion is transferred from a lattice site to an interstitial position in a Frenkel defect.
$IV.$ The density of a crystal always increases due to a substitutional impurity defect.

The setting of cement is an ....... process.

Select the correct statement.

$A$ body-centred cubic $(BCC)$ element of density $10.3 \ g \ cm^{-3}$ has a cell edge of $314 \ pm$. Calculate the atomic mass of the element. Also, Lithium borohydride crystallizes in an orthorhombic system with four molecules per unit cell. The unit cell dimensions are $a = 6.8 \ \mathring{A}$, $b = 4.4 \ \mathring{A}$, and $c = 7.2 \ \mathring{A}$. If the molar mass is $21.76 \ g \ mol^{-1}$, calculate the density of the crystal.