Class 12 Chemistry: CBSE Marking Scheme (2024-25)

 Page 1


MARKING SCHEME
SAMPLE P APER (2024 -25)
CHEMISTR Y THEOR Y
(043)
S E C T I O N A 1 (c) reacts with Benzenesulphonyl chloride to form a product that is
insoluble in alkali
1
2 (b)CH
3
Cl
The order followed is this CH
3
I<CH
3
Br<CH
3
F< CH
3
Cl , though F is
most electronegative, the bond length is small as compared to C-Cl.
Dipole moment is the product of the charge and the bond length.
1
3 (a) (i)-(C), (ii)-(B), (iii)-(A) 1
4 (d) 1 =Bromomethane, 2= 2-Bromo-2-methylpropane, 3=2-
Bromobutane, 4= 1-Bromobutane
( f o r v i s u a l l y c h a l l e n g e d l e a r n e r s ) d. 1-Bromobutane
1
1
5 (c) the order of reaction is zero as the unit of k is molL
-1
s
-1
. Thus half
life = [R]
o
/ 2k = 4.62 x 10
-2
/2 x 2.31 x 10
-2
1
6 (b) Benzoic acid and ethanoic acid
C
6
H
5
COOCOCH
3
H
2
O C
6
H
5
COOH + CH
3
COOH
1
7 (b) X=[Co(NH
3
)
4
Cl
2
]
+
Cl
-
, Y= 1:3 1
8 (b) Cellulose
Starch contains only a glucose, sucrose contains a-D-glucose and
ß-D-fructose glucose, maltose contains a-D-glucose and cellulose is a
polymer of ß-D-glucose.
1
9 (d) Ti
3+
< Cr
3+
< Fe
2+
< Mn
2+
No. of unpaired electrons : Ti
3+
(1), Cr
3+
(3), Fe
2+
(4) and Mn
2+
(5)
Paramagnetism depends on the number of unpaired electrons
1
10 (d) It never goes to completion
First order reaction [R] = [Ro] e
-kt
If [R]=0 then
1
1
Page 2


MARKING SCHEME
SAMPLE P APER (2024 -25)
CHEMISTR Y THEOR Y
(043)
S E C T I O N A 1 (c) reacts with Benzenesulphonyl chloride to form a product that is
insoluble in alkali
1
2 (b)CH
3
Cl
The order followed is this CH
3
I<CH
3
Br<CH
3
F< CH
3
Cl , though F is
most electronegative, the bond length is small as compared to C-Cl.
Dipole moment is the product of the charge and the bond length.
1
3 (a) (i)-(C), (ii)-(B), (iii)-(A) 1
4 (d) 1 =Bromomethane, 2= 2-Bromo-2-methylpropane, 3=2-
Bromobutane, 4= 1-Bromobutane
( f o r v i s u a l l y c h a l l e n g e d l e a r n e r s ) d. 1-Bromobutane
1
1
5 (c) the order of reaction is zero as the unit of k is molL
-1
s
-1
. Thus half
life = [R]
o
/ 2k = 4.62 x 10
-2
/2 x 2.31 x 10
-2
1
6 (b) Benzoic acid and ethanoic acid
C
6
H
5
COOCOCH
3
H
2
O C
6
H
5
COOH + CH
3
COOH
1
7 (b) X=[Co(NH
3
)
4
Cl
2
]
+
Cl
-
, Y= 1:3 1
8 (b) Cellulose
Starch contains only a glucose, sucrose contains a-D-glucose and
ß-D-fructose glucose, maltose contains a-D-glucose and cellulose is a
polymer of ß-D-glucose.
1
9 (d) Ti
3+
< Cr
3+
< Fe
2+
< Mn
2+
No. of unpaired electrons : Ti
3+
(1), Cr
3+
(3), Fe
2+
(4) and Mn
2+
(5)
Paramagnetism depends on the number of unpaired electrons
1
10 (d) It never goes to completion
First order reaction [R] = [Ro] e
-kt
If [R]=0 then
1
1
e
-kt
= 0, which is not possible for any finite value of t. Here, t is 8.
11 (a) Nitrobenzene 1
12 (a)CH
3
COCH
3
Aldehyde and ketones give nucleophilic addition reactions. Other
carbonyl compounds do not give nucleophilic addition reactions.
1
13 (a) Both A and R are true and R is the correct explanation of A 1
14 (d) A is false but R is true.
is an incorrect equation, the correct equation is
1
15 (b) Both A and R are true but R is not the correct explanation of A.
Due to the absence of a free aldehydic group, it does not give a
reaction with NaHSO
3
.
1
16 (d)A is false but R is true.
The half- life for a zero order reaction t
1/2
= [Ro]/2k where [Ro] is the
initial concentration of the reactant.
1
S E C T I O N B 17 (a) Solubility of gas is inversely proportional to the value of Henry's
constant K
H
. On increasing temperature nitrogen gas becomes less
soluble because its K
H
value increases.
(b) (ii)64.5
o
C
Chloroform and acetone mixture show negative deviation from
Raoult’s law therefore, they form maximum boiling azeotrope at a
specific composition. The boiling point of the mixture so obtained
will be higher than the individual components.
O R (a) At higher altitudes i.e. in Srinagar the atmospheric pressure is
½
½
½
½
1
2