Question Set E

cbse 12th Standard Chemistry Biomolecules Important Questions And Answers Study Material - QB365

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Questions:

Generic 3

7 x 3 = 21

What happens when:
(i) Ethanol is treated with Cu at 573 K.
(ii) Phenol is treated with CH₃COCl / anhydrous AlCl₃.
(iii) Ethyl chloride is treated with NaOCH₃?

Which one of the following has the highest dipole moment?
(i) CH₂Cl₂
(ii) CHCl₃
(iii) CCl₄

Write the important structural and functional differences between DNA and RNA

Calculate the equilibrium constant for the reaction at 298 K:
4 Br^- + O₂ + 4 H⁺ \(\longrightarrow\) 2 Br₂+ 2 H₂O . Given that E⁰ cell = 0.16 V.

What happens when:
(i) An aqueous solution of sodium acetate is electrolysed?
(ii) Calcium acetate is dry distilled?
(iii) Sodium benzoate is heated with soda lime?

The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:

Experiment	[A]/mol L^-1	[B]/mol L^-1	Initial rate in mol L^-1 min^-1
I	0.1	0.1	2.0 \(\times\) 10^-2
II	-----	0.2	4.0 \(\times\) 10^-2
III	0.4	0.4	-----
IV	-----	0.2	2.0 \(\times\) 10^-2

An aqueous solution of 3.12 g of BaCl₂in 250 g of water is found to boil at 100.0832^oC. Calculate the degree of dissociation of BaCl₂. [K _b(H₂O) = 0.52 K/m.]

Generic 5

3 x 5 = 15

Arrange the following:
(i) In decreasing order of the pKb values:
C₂H₅NH₂, C₆H₅NHCH₃, (C₂H₅)2NH and C₆H₅NH₂
(ii) In increasing order of basic strength:
C₆H₅NH₂, C₆H₅N(CH₃)₂,(C₂H₅)₂NH and CH₃NH₂
(iii) In increasing order of basic strength:
(a) Aniline, p-nitroaniline and p-toluidine
(b) C₆H₅NH₂, C₆H₅NHCH₃, C₆H₅CH₂NH₂.
(iv) In decreasing order of basic strength in gas phase:
C₂H₅NH₂, (C₂H₅)₂NH, (C₂H₅)₃N and NH₃
(v) In increasing order of boiling point:
C₂H₅OH, (CH₃)₂NH, C₂H₅NH₂
(vi) In increasing order of solubility in water:
C₆H₅NH₂, (C₂H₅)₂NH, C₂H₅NH₂.

Write down the number of 3d electrons in each of the following ions: Ti²⁺, V²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺ and Cu²⁺. Indicate how would you expect the five 3d orbitals to be occupied for these hydrated ions (octahedral).

10.

Explain how rusting of iron is envisaged as setting up of an electrochemical cell.

Generic 2

5 x 2 = 10

11.

Name the compound with molecular formula C₇H₈O which on treatment with Br₂ water, readily gives a precipitate of C₇H₅OBr_3.

12.

Explain the following terms:
(i) Rate constant (k)

13.

Deficiency of which vitamin causes beri-beri and pain in joints ?

14.

How will you prepare bromobenzene from aniline ?

15.

Give the IUPAC names of the following compounds:
(i) Ph CH₂CH₂COOH
(ii) (CH₃)₂C=CHCOOH
(iii)

(iv)

Multiple Choice Question

16 x 1 = 16

16.

Which of the following is a polysaccharide?

(a)

Glucose

(b)

Maltose

(c)

Glycogen

(d)

Lactose

17.

THe electrophile involved in Riemer-Tiemann reaction of phenol with CHCI₃ in presence of NaOH is

(a)

:CCl ₂

(b)

\(\stackrel{\ominus}{C} C_{3}\)

(c)

\(\stackrel{\oplus}{\mathrm{CHO}} \)

(d)

\(\stackrel{\oplus}{\mathrm{C}} \mathrm{HCl}_{2}\)

18.

'X', X is

(a)

(b)

(c)

(d)

19.

The complex ion having minimum magnitude of \(\triangle\)_o(CFSE) is

(a)

[CO(NH₃)₆]³⁺

(b)

[Cr(H₂O)₆]³⁺

(c)

[Cr(CN)6]^3-

(d)

[CoCl₆]^3-

20.

Efficiency of fuel cell is equal

(a)

\(\frac{\Delta \mathrm{G}}{\Delta \mathrm{S}}\)

(b)

\(\frac{\Delta \mathrm{G}}{\Delta \mathrm{H}}\)

(c)

\(\frac{\Delta \mathrm{S}}{\Delta \mathrm{G}}\)

(d)

\(\frac{\Delta \mathrm{H}}{\Delta \mathrm{G}}\)

21.

4L of 0.02 M aqueous solution of NaCI was diluted by adding one litre of water. The molality of the resultant solution is ________________.

(a)

0.004

(b)

0.008

(c)

0.012

(d)

0.016

22.

Name the product(s) formed during the reaction of primary aliphatic amines with nitrous acid at room temperature?

(a)

\(\begin{equation} R \mathrm{~N}_{2}^{+} \mathrm{Cl^-} \end{equation}\)

(b)

ROH

(c)

Both (a) and (b)

(d)

None of the above

23.

Consider the following statements

(I) La(OH)₃ is least basic among hydroxides of lanthanides

(II) Zi⁴⁺ and Hf⁴⁺ possess almost the same ionic radii

(III) Ce⁴⁺ can act as an oxidizing agent

Which of the above is/are true ?

(a)

(I) and (III)

(b)

(II) and (III)

(c)

(II) only

(d)

(I) and (II)

(e)

(I) only

24.

In chromite ore, the oxidation number of iron and chromium are respectively

(a)

+3, +2

(b)

+3, +6

(c)

+2, +6

(d)

+2, +3

25.

If the enolate ion combines with the carbonyl group of an ester, we get

(a)

aldol

(b)

\(\alpha ,\beta\) - unstaurated ester

(c)

\(\beta\) - ketoaldehyde

(d)

acid

26.

The correct order of basic strength is

(a)

H₂O<OH^-<CH₃O^-

(b)

CH₃OH<H₂O<CH₃O^-<OH^-

(c)

H₂O<CH₃OH<OH^-<CH₃O^-

(d)

OH^-H₂O<CH₃O^-<CH₃OH

27.

Zn gives H₂ gas with H₂SO₄ and HCl but not with HNO₃ because

(a)

Zn acts as oxidizing agent when reacts with HNO₃

(b)

HNO₃ is weaker acid than H₂SO₄ and HCl

(c)

In electrochemical series, Zn is above hydrogen

(d)

NO₃^- is reduced in preference to hydronium ion

28.

Which of the following possesses highest melting point?

(a)

Chlorobenzene

(b)

o-Dichlorobenzene

(c)

m-Dichlorobenzene

(d)

p-Dichlorobenzene

29.

The non-existent metal carbonyl among the following is

(a)

Cr(CO)₆

(b)

Mn(CO)₅

(c)

Ni(CO)₄

(d)

Fe(CO)₅

30.

For the first order reaction
2 N₂O₅ (g) \(\longrightarrow\) 4 NO₂ (g) + O₂ (g)

(a)

the concentration of the reactant decreases exponentially with time

(b)

the half-life of the reaction decreses with increases temperature

(c)

the half-life of the reaction depends on the initial concentration of the reactant

(d)

the reaction proceeds to 99/6% completion in eight half-duration

31.

The system that forms maximum boiling azeotrope is

(a)

carbon disulphide-acetone

(b)

benzene-tolune

(c)

acetone-chloroform

(d)

n-hexane-n-heptane

Case Study Questions

2 x 4 = 8

32.

Read the passage given below and answer the following questions:
The phenomenon of the flow of solvent through a semipermeable membrane from pure solvent to the solution is called osmosis.
Sometimes a pressure is applied to stop the process of osmosis, this is known as osmotic pressure. It is denoted by \(\pi \). Osmotic pressure is expressed as: \(\pi \) = CRT
Since, osmotic pressure depends upon the molar concentration of solution, therefore it is a colligative property.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: If red blood cells were removed from the body and placed in pure water, pressure inside the cells increases.
Reason: The concentration of salt content in the cells increases.
(ii) Assertion: When a solution is separated from the pure solvent by a semipermeable membrane, the solvent molecules pass through it from pure solvent side to the solution side.
Reason: Diffusion of solvent occurs from a region of high concentration to a region of low concentration solution.
(iii) Assertion: Two solutions having same osmotic pressure at a given temperature are called isotonic solutions.
Reason: Osmotic pressure is not a colligative property.
(iv) Assertion: The preservation of meat by salting and fruits by adding sugar protects against bacterial action.
Reason: A bacterium on salted meat or candid fruit loses water due to osmosis shrivels and ultimately dies.

33.

Read the passage given below and answer the following questions:
Arrangement of ligands in order of their ability to cause splitting Δ is called spectrochemical series. Ligands which cause large splitting (large Δ ) are called strong field ligands while those which cause small splitting (small Δ) are called weak field ligands. When strong field ligands approach metal atomlion, the value of Δ_o is large, so that electrons are forced to get paired up in lower energy t_2g orbitals. Hence, a low-spin complex is resulted from strong field ligand. When weak field ligands approach metal atom/ion, the value of Δ_o is small, so that electrons enter high energy e_g orbitals rather than pairing in low energy t_2g orbitals. Hence, a high-spin complex is resulted from weak field ligands. Strong field ligands have tendency to form inner orbital complexes by forcing the electrons to pair up. Whereas weak field ligands have tendency to form outer orbital complex because inner electrons generally do not pair up.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: In tetrahedral coordination entity formation, the d orbital splitting is inverted and is smaller as compared to the octahedral field splitting.
Reason: Spectrochemical series is based on the absorption of light by complexes with different ligands.
(ii) Assertion: F^- ion is a weak field ligand and forms outer orbital complex.
Reason: F^- ion cannot force the electrons of d_z2 and d_{x²- y²}orbitals of the inner shell to occupy d_xy, d_yz and d_zx orbitals of the same shell.
(iii) Assertion: The crystal field model is successful in explaining the formation, structures, colour and magnetic properties of coordination compounds.
Reason: In spectrochemical series, ligands are arranged in a series of increasing field strength.
(iv) Assertion: NF₃ is a weaker ligand than N(CH₃)_3.
Reason: NF₃ ionizes to give F^- ions in aqueous solution.

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Answers Key:

Generic 3

7 x 3 = 21

Dichloromethane has highest dipole moment among CH₂Cl₂, CHCl₃ and CCl₄. The decreasing order of dipole moments is CH₂Cl₂>CHCl₃>CCl₄. These molecules have tetrahedral geometry due to sp3 hybridization of carbon atom.In CCl4, the individual C−Cl bond dipoles cancel each other which results in zero dipole moment.
Hence, CCl₄ is non polar.

**Structural differencee**
S.No	DNA	RNA
1	The sugar present in DNA is 2-deoxy-D-(-)-ribose.	The sugar present in ~A is D-(-)-ribose.
2	DNA contains cytosine and thymine as pyrimidine bases.	RNA contains cytosine and uracil as pyrimidine bases.
3	DNA has double stranded u-helix structure.	RNA has single stranded \(\alpha \)-helix structure.
4	DNA molecules are very large; their molecular mass may vary from \(6\times { 10 }^{ 6 }-16-{ 10 }^{ 6 }u\) ,i.e., from six to sixteen million.	RNA molecules are much smaller with molecular mass ranging from 20,000 to 40,000 u.

Functional difference
1. DNA has unique property of replication.	1. RNA usually does not replicate.
2. DNA controls the transmission of hereditary effects.	2. RNA controls the synthesis of prote

6.747 \(\times\) 10¹⁰

(i) \(2CH_{ 3 }COONa\overset { Electrolysis }{ \longrightarrow } 2CH_{ 3 }COO^{ - }+2Na^{ + }\)

At anode : \(2CH_{ 3 }COO^{ - }\longrightarrow \overset { CH_{ 3 } }{ \underset { CH_{ 3 } }{ | } } +2CO_{ 2 }+2e^{ - }\)
At Cathode : \(2H^++2e^-\rightarrow H_2(g)\)
(ii) \(_{ CH_{ 3 }COO }^{ CH_{ 3 }COO }{ _{ \diagup }^{ \diagdown }{ Ca } }\quad \overset { Dry }{ \underset { distillation }{ \longrightarrow } } \underset { Acetone }{ CH_{ 3 }COCH_{ 3 } } +CaCO_{ 3 }\)
(iii) \(\underset { Sodium\quad benzoate }{ C_{ 6 }H_{ 5 }COONa } +\underset { Soda\quad lime }{ NaOH(CaO) } \overset { \triangle }{ \longrightarrow } \underset { Benzene }{ C_{ 6 }H_{ 6 } } +\underset { sodium\\ carbonate }{ Na_{ 2 }CO_{ 3 } } \)

\(\frac { dx }{ dt } =k{ \left[ A \right] }^{ 1 }{ \left[ B \right] }^{ 0 }\)
\(\\ From \ expt. \ I\)
\(2.0\times { 10 }^{ -2 }=k\left[ 0.1 \right] ,\)
\(k=2.0\times { 10 }^{ -1 }{ min }^{ -1 }\)
\(=0.2{ \ min }^{ -1 }=2\times { 10 }^{ -1 }{ min }^{ -1 }\)
\(In \ expt. \ II\)
\(\frac { dx }{ dt } =k{ \left[ A \right] }^{ 1 }\)
\(4\times { 10 }^{ -2 }=2\times { 10 }^{ -1 }\times \left[ A \right]\)
\(\Rightarrow \ \left[ A \right] =0.2 \ mol \ { L }^{ -1 }\)
\(In \ expt. \ III\)
\(Rate=\frac { dx }{ dt } =k{ \left[ A \right] }\)
\( =1.2\times 0.4\)
\(=8\times { 10 }^{ -2 }mol \ { L }^{ -1 }{ min }^{ -1 }\)
\(In \ expt.IV\)
\(2.0\times { 10 }^{ -2 }=0.2\times \left[ A \right]\)
\(\left[ A \right] =0.1mol \ { L }^{ -1 }\)

ΔT_b = 100.0832 - 100.0 = 0.0832°C,
K_b = 0.52 K kg mol^-1,
W_A = 250 g, W_B = 3.12 g,
M_B = 137 + 71 = 208 9 mol^-1
Now \(ΔT_b=iK_b\times{W_B\over M_B}\times{1000\over W_A}\)
⇒ \(0.0832 = i \times 0.52 \times{3.12\over4 6.489}\times{1000\over 250}\)
\(⇒ i={0.0832\times208\over 4\times3.12\times0.52}={17.30\over 6.489}=2.66\)
\(\alpha={i-1\over n-1}={2.66-1\over 3-1}={1.66\over 2}=0.83\)
Degree of dissociation (α) = 83%

Generic 5

3 x 5 = 15

(i) Stronger base has lower pK_b value.
C₆H₅NH₂>C₆H₅NHCH₃>C₂H₅NH₂>(C₂H₅)₂NH
(ii) Increasing order of basicity is as follows:
C₆H₅NH₂6H₅NHCH₃3NH₂<(C₂H₅)₂NH
(iii) Increasing order of basic strength.
(a) p-nitroaniline < aniline < p-toluidine
(b) PhNH₂32NH₂
(iv) In decreasing order of basic strength in gas phase:
Et₃N>Et₂NH>EtNH₂>NH₃
The stabilization of conjugate acids due to hydrogen bonding is absent.
(v) Increasing order of boiling point
Me₂NH2 (vi) Increasing order of solubility in water:
PhNH₂2NH2

Metal ion	Number of d-electrons	Filling of d-orbitals
Ti²⁺	2	\(t_{2 g}^{2}\)
V²⁺	3	\(t_{2 g}^{3}\)
Cr³⁺	3	\(t_{2 g}^{3}\)
Mn²⁺	5	\(t_{g}^{3} e_{g}^{2}\)
Fe²⁺	6	\(t_{2 g}^{4} e_{g}^{2}\)
Fe³⁺	5	\(t_{2 g}^{3} e_{g}^{2}\)
CO²⁺	7	\(t_{2 g}^{5} e_{g}^{2}\)
Ni²⁺	8	\(t_{2 g}^{6} e_{g}^{2}\)
Cu²⁺	9	\(t_{2 g}^{6} e_{g}^{3}\)

10.

In process of rusting, water molecules present at the layer of iron react with oxides and get dissociated and give H⁺ ions
H₂O + CO₂ → H₂CO₃
H₂CO₃↔ 2H⁺ + CO₃^2–
In present of H⁺ ions iron convert in Fe2+ so this part is act as anode
Reaction at anode:
Fe(s) → Fe²⁺(aq) + 2e^–
Electron released at anodic spot move through the metals and go to another spot on the metal and reduce oxygen this spot act as cathode
Reaction at Cathode:
O₂(g) + 4H⁺(aq) + 4e⁺( aq) → 2H₂O(l)
The overall reaction
2Fe(s) + O₂(g) + 4H⁺(aq) → 2H₂O(l) + Fe²⁺(aq)
Hence, rusting of iron act as electrochemical cell.

Generic 2

5 x 2 = 10

11.

C₆H₅CH₂OH

12.

(i) Rate constant (k): Rate constant is rate of the reaction when the concentration of reactants is unity.

13.

Vitamin B₁.

14.

15.

i) PhCH₂CH₂COOH
3-Phenylpropanoic acid
ii) (CH₃)₂C = CHCOOH
3-Methylbut-2-enoic acid
iii) 2-Methylcyclopentane carboxylic acid
iv) 2,4,6-Trinitrobenzoic acid

Multiple Choice Question

16 x 1 = 16

16.

17.

(a)
:CCl ₂

18.

19.

(d)
[CoCl₆]^3-

20.

(b)
\(\frac{\Delta \mathrm{G}}{\Delta \mathrm{H}}\)

21.

(d)
0.016

22.

(b)
ROH

23.

(b)
(II) and (III)

24.

(d)
+2, +3

25.

26.

27.

(d)
NO₃^- is reduced in preference to hydronium ion

28.

(d)
p-Dichlorobenzene

29.

(b)
Mn(CO)₅

30.

(d)
the reaction proceeds to 99/6% completion in eight half-duration

31.

Acetone-chloroform mixture shows negative deviation from Raoult's law. Hence, for a particular composition, it has lowest vapour pressure and maximum boiling point.

Case Study Questions

2 x 4 = 8

32.

(i) (c) :If the red blood cells are placed in pure water, pressure inside the cells increases as the water is drawn in and the cell swells.
(ii) (b)
(iii) (c) : Osmotic pressure is a colligative property
(iv) (a)

33.

(i) (b)
(ii) (a)
(iii) (b)
(iv) (c): Due to high electronegativity of F^-atoms, the lone pair of N^-atom in NF₃ molecule cannot be ligated easily. Whereas in N(CH₃)_3'CH₃ group is a electron releasing group, thus lone pair of N-atom in N(CH3)3 molecule can be ligated easily.

Except, nitrogen fluoride, all other halides hydrolyse in water.