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प्रश्न
Why ionic crystals are hard and brittle?
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उत्तर
The ionic compounds are very hard and brittle. In ionic compounds, the ions are rigidly held in a lattice because the positive and negative ions are strongly attracted to each other and difficult to separate. But the brittleness of a compound is now easy to shift the position of atoms or ions in a lattice.
If we apply pressure on the ionic compounds the layers shifts slightly. The same charged ions in the lattice come closer. A repulsive force arises between the same charged ions, due to this repulsion the lattice structure breaks down chemical bonding.
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संबंधित प्रश्न
Describe triclinic crystal lattice with the help of a diagram.
How will you distinguish between the following pair of terms?
Crystal lattice and unit cell
Name the parameters that characterize a unit cell.
An ionic crystal lattice has limiting value of radius ratio as 0.414 to 0.732; the co-ordination number of its cation is _______.
(A) 6
(B) 4
(C) 3
(D) 12
Which of the following parameters are correct for triclinic lattice?
(A) α = β = γ = 90° and a = b = c
(B) α ≠ β ≠ γ = 90° and a ≠ b ≠ c
(C) α = γ = 90°, β ≠ 90° and a ≠ b ≠ c
(D) α ≠ β ≠ γ ≠ 90° and a ≠ b ≠ c
Calculate the number of atoms present in 2 gram of crystal which has face-centred cubic
(FCC) crystal lattice having edge length of 100 pm and density 10 gcm−3
An ionic crystal lattice has `r^+/r` radius ratio of 0.320, its coordination number is __
(a) 3
(b) 4
(c) 6
(d) 8
i)
Consider the following cell reaction at 298 K: [3]
2Ag+ + Cd → 2Ag + Cd2+
The standard reduction potentials (E°) for Ag+/Ag and Cd2-/Cd are 0.80 V and -0.40 V respectively:
(1) Write the cell representation.
(2) What will be the emf of the cell if the concentration of Cd2+ is 0.1M and that of Ag+ is 0.2 M?
(3) Will the cell work spontaneously for the condition given in (2) above?
(ii)
What is a buffer solution? How is it prepared? Explain the buffer action of a basic buffer with a suitable example.
In a crystal of diamond:
- How many carbon atoms are present per unit cell?
- What type of lattice does diamond crystallise in?
- How many carbon atoms surround each carbon atom?
- How are they arranged?
How many three-dimensional crystal lattices are possible?
