MS CLASS XII CHEMISTRY 2
Q VALUE POINTS MARKS
NO
.
SECTION -A (MCQ)
1. (b) 1:2:4 1
2. 1
(d) f-centres
3. i) Methanol and acetone 1
4. (i) K kg mol–1 or K (molality)–1 1
5 (ii) Cu is cathode 1
6 (iii) Conductivity does not depend upon solvation of ions present in solution 1
7 (B) Frenkel defect 1
8 (a) 1 M glucose 1
9. (d) both (a) and (b) 1
10 (d) PT≠P1+P2 1
11. (c)(iii) 1
12. (b)(ii) 1
13 (a) (i) 1
14. In face centred cubic unit cell (fcc) : 2
r = a/ 2 √2
a = 408 pm
r = 408/2 √2
r = 144 pm
Diameter = 2r = 2×144 = 288 pm
15.
For hydrogen electrode, , it is given that pH = 10
∴[H+] = 10 - 10M
Now, using Nernst equation:
= - 0.0591 log 1010
= - 0.591 V
16. (i) (a) increases with increase in temperature. 1
(ii) (b) 32.1% oxygen 1
(iii) (b)greater for gases with lower solubility. 1
SECTION - B
17. Given that , 2
κ = 0.0248 S cm−1 and c = 0.20 M
Formula of molar conductivity,
Λm = ( k × 1000)/M
Λm =(0.0248 × 1000 )/0.2
Λm =124 S cm2 mol−1
18. For strong electrolytes - the molar conductivity increases slowly with the dilution. The
plot between the molar conductivity and C1/2 is a straight line having y-intercept equal
to Λm ° The value of limiting molar conductivity, Λm ° can be determined from the
graph or with the help of Kohlrausch law. The general equation for the plot is given as:
Ʌm = Λm °-A C1/2
Where -A is a constant equal to the slope of the line. For a given solvent, the value of
“A” depends on the type of electrolyte at a particular temperature.
For weak electrolytes - Weak electrolytes have lower molar conductivities and lower
degree of dissociation at higher concentrations which increases steeply at lower
concentrations. Therefore, limiting molar conductivity, Λm ° cannot be obtained by
extrapolation of molar conductivity to zero concentration. Hence, we use Kohlrausch
law of independent migration of ions for determining to limit molar conductivity of weak 3
electrolytes.
19 From the equation, density = ZxM/a3 x N0, we get
M = ρ x a3 x N0/Z
Placing the values
M= 10.5 x (4.077 x10-8)3 x 6.022 x 1023/4
= 107.1 gmol-1
= Therefore, atomic mass of silver = 107.1 gmol-1
20
21. (a) (i) Frenkel defect (i) both schottky and frenkel defect 1+1
(b) (i) 14 1
(ii) 14 1
(iii) 9 1
OR
(a) A4B3 2
3
22. (a) 3
(b) (i) one correct function
(ii) Cell constant is of particular cell is determined as the ratio of the distance 1
between the electrodes of the cell to the area of the electrodes. 1
cell constant
OR
(a) (i) Silver wire at 30˚C because metallic conduction decrease with increase 1
in temp .due to vibration of kernels.
(ii) 0.1 M acetic acid solution because with dilution degree of dissociation 1
increases and hence number of ions increase.
(iii) KCl solution at 50C because conductivity increase with rise in 1
temperature
Electrochemical cell Ectrolytic cell
Electrochemical cells convert Electrolytic cell is a type of
chemical energy into electrical electrochemical cell in which electrical
energy or vice versa. energy is converted into chemical energy.
Electrochemical cells consist of a Electrolytic cells consist of positively
cathode (+) and an anode(-). charged anode and a negatively charged
cathode.
(b)
2
