AHSEC| CLASS 12| CHEMISTRY| SOLVED PAPER - 2024| H.S. 2ND YEAR
2024
CHEMISTRY
(THEORY)
Full Marks: 70
Pass Marks: 21
Time: Three hours
The figures in the margin indicate
full marks for the questions.
1. What is the molarity of a solution containing 5g of NaOH in 450ml solution? 1
Ans:-
2. How much H2 in grams will be liberated if
1F electricity is passed through acidified water? 1
Ans:- When 1 Faraday (F) of electricity is passed
through acidified water, the electrolysis reaction produces hydrogen gas (H2).
According to Faraday's laws of electrolysis, 1 Faraday liberates about 1 mole
of H2. The molecular weight of H2 is about 2 g/mol.
Therefore,
the mass of hydrogen liberated is:
Mass = mol × molar
mass = 1 mole × 2g Mol = 2g
Hence, 2 g of H2
will be liberated.
3. Identify the reaction order from the following rate
constants: 1
k= 2.3 × 10–5
l mol-1 s-1
Ans:-Reaction order from rate constant:-
The rate constant
k=2.3×10 −5 lmol −1 s −1 indicates that
the reaction is second order. This is because the units for a second order
reaction are lmol −1 s −1, which matches the given
rate constant.
4. Which of the 3d transition metals exhibits the largest
number of oxidation states? 1
Ans:- Transition metals with the highest oxidation
states:-
Among the 3d
transition metals, manganese (Mn) exhibits the highest number of oxidation
states, ranging from -3 to +7. This versatility arises from its electronic
configuration and its ability to lose varying numbers of electrons.
5. Write the chemical formula for the following
coordination compounds: 1
Mercury (I)
tetrathiocyanato-s-cobaltate (III)
Ans:-
6. In the following pairs of halogen compounds, which
would undergo SN2 reaction faster? 1
Ans:- (i) It is a primary halide and hence the SN2
reaction is faster.
(ii) Since
iodine is a better leaving group due to its larger size, it will be released at
a faster rate in the presence of an incoming nucleophile.
7. Write the products that are formed by heating of the
following ether with HI: 1
Ans:-
8. What is the basic structural difference between starch
and cellulose? 1
Ans:- Structural Difference Between Starch and
Cellulose:-
Linkage Type:
The primary structural difference between starch and cellulose lies in the type
of glycosidic linkages between their glucose units. Starch contains
α-D-glycosidic linkages, resulting in a branched structure (in the case of
amylopectin) and a helical structure (in amylose). In contrast, cellulose is
composed of β-D-glycosidic linkages, which form long, linear chains that allow
for strong hydrogen bonding between adjacent chains, which contributes to its
stiffness and strength.
9. Diazonium salts of aromatic amines are more stable
than those of aliphatic amines. Why? 2
Ans:- Stability of Diazonium Salts:-
Stability
Comparison: Diazonium salts derived from aromatic amines are more stable
than diazonium salts derived from aliphatic amines due to resonance
stabilization provided by the aromatic ring. In aromatic diazonium salts, the
positive charge on the π-electron system of the aromatic ring can be displaced.
This delocalization stabilizes the diazonium ion. In contrast, aliphatic
diazonium salts lack such resonance stabilization, making them more reactive
and less stable.
Or
Why do
primary amines have higher boiling point than tertiary amines? 2
Ans:- Boiling
Point of Amines:-
Boiling
Point Difference: Primary amines generally have higher boiling points than
tertiary amines, because of their ability to form stronger hydrogen bonds.
Primary amines have two hydrogen atoms bonded to the nitrogen, allowing for
more extensive hydrogen bonding with other molecules than tertiary amines,
which have no hydrogen atoms attached to the nitrogen. This increased hydrogen
bonding in primary amines leads to a higher boiling point than tertiary amines.
10. Calculate the equilibrium constant of the reaction: 2
Cu (s) + 2Ag+
(aq) → Cu2+ (aq) + 2Ag(s)
Ans:-
Or
Write the
Nernst equation and emf of the following cells at 298K: 2
(i) Mg(s)|Mg2+
(0.001M) || Cu2+ (0.0001M) Cu(s)
(ii) Sn(s)|Sn2+
(0.050M) || H+ (0.020M)|H2 (g) (1bar)|Pt (s)
Ans:-
11. Define conductivity and molar conductivity for the
solution of an electrolyte. Discuss their variation with concentration. 2
Ans:- Definition of Conductivity and Molar Conductivity:-
Conductivity
(κ): It is a measure of the ability of a solution to conduct
electric current, which depends on the concentration of free ions in the
solution. It is defined as the ratio of current density to the strength of the
electric field. Conductivity is usually expressed in units of siemens per meter
(S/m).
Molar
Conductivity (Λm): It refers to the conductivity of an electrolyte
solution per mole of solute. It is defined as the conductivity multiplied by
the volume of the solution divided by the number of moles of solute. Molar
conductivity is expressed in units of siemens meter squared per mole (S
m²/mol).
Variation
with Concentration:-
The behaviour
of conductivity and molar conductivity with respect to concentration may be
summarized as follows:-
(i) Conductivity:-
(a) Initially
increases with increase in electrolyte concentration due to greater number of
free ions available for conduction.
(b) At high
concentrations, conductivity may reach a maximum value and then stabilize or
increase at a slower rate. This occurs because ions begin to form ion pairs,
which reduces the number of effective charge carriers and reduces mobility due
to increased interactions between ions.
(ii) Molar
Conductivity:-
(a) Molar
conductivity generally decreases with increasing concentration after a certain
point. This is because, although more ions are present, their mobility is
reduced due to increased ionic interactions and the possible formation of ion
pairs, which hinders their ability to contribute effectively to conduction.
In short,
while both conductivity and molar conductivity initially increase with
concentration, their behavior diverges at higher concentrations due to physical
interactions between ions in solution.
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