Chemistry RBSE Paper 2024 Solution

SECTION -A

Multiple Choice Questions :

1) Write the answer of following multiple choice questions in the given answer book

i) SI unit of conductivity is –

(A) S

(B) Ω

(C) Scm^-1

(D) Sm^-1

Ans (D) Sm^-1

ii) Element showing the highest number of oxidation states is –

(A) Mn

(B) Ni

C) Fe

(D) Cr

Ans (A) Mn

iii) Oxidation state of Fe in [Fe(Co)₅] is-

(A) 0

(B) +2

(C) +3

(D) +4

Ans (B) +2

iv) The chemical formula of chromite ore is –

(A) MnO₂

(B) Na₂Cr₂0₄

(C) FeCr₂0₄

(D) Na₂CrO₄

Ans (C) FeCr₂0₄

v) Number of moles of precipitated AgCl on adding excess silver nitrate solution in the solution of one mole of CoCl₃.5NH₃ is –

(A) 1

(B) 2

(C) 3

(D) 5

Ans (C) 3

vi) Metal present in haemoglobin is –

(A) Mn

(B) Fe

(C) Co

(D) Ni

Ans (B) Fe

vi) Ambidentate ligand is –

(A) Cl^–

(B) H₂O

(C) NH₃

(D) NO₂^–

Ans (D) NO₂^–

vii) The compound obtained from meadow sweet is –

(A) Salicyl aldehyde

(B) Cinnamaldehyde

(C) Valeraldehyde

(D) Vanillin

Ans (A) Salicyl aldehyde

ix) IUPAC name of

(A) Phthalic acid

(B) Benzene -1, 2- dicarboxylic acid

(C) Benzene -1, 2-dioic acid

(D) Phenyl -1, 2- dicarboxylic acid

Ans (C) Benzene -1, 2-dioic acid

x) Change occurs in hybridisation state of carbonyl carbon in nucleophilic addition reaction is –

(A) sp² to sp

(B) sp to sp²

(C) sp² to sp³

(D) sp³ to sp²

Ans (A) sp² to sp

xi) The hybridisation state of nitrogen intrimethylamine is-

(A) sp

(B) sp²

(C) sp³

(D) dsp²

Ans (C) sp³

xii) The compound showing highest basic strength in aqueous solution is –

(A) (C₂H₅)₃N

(B) (C₂H₅)₂NH

(C) C₂H₅NH₂

(D) NH₃

Ans (D) NH₃

xiii) Secondary amine among the following is –

(A) Propan -2- amine

(B) Pentan -3-amine

(C) N-Methylethanamine

(D) N,N- Dimethylmethanamine

Ans (D) N,N- Dimethylmethanamine

xiv) Globular protein is –

(A) Insulin

(B) Keratin

(C) Myosin

(D) Collagen

Ans (A) Insulin

xv) Glucose is –

(A) An aldopentose

(B) A ketopentose

(C) An aldohexose

(D) A ketohexose

Ans (C) An aldohexose

xvi) Milk sugar is –

(A) Sucrose

(B) Lactose

(C) Maltose

(D) Galactose

Ans (B) Lactose

2) Fill in the blanks

i) The unit of molarity is …………………..

Ans moles per liter, ( mol/L)

ii)The mathematical form of Henry’s Law is………………………..

Ans C= K_H.P

iii) The kinetic energy of maximum fraction of reactant molecules is called …………….

Ans Activation Energy

iv) …………………and actinoids are called as inner transition elements.

Ans Lanthanoids

v) …………………is coordination sphere in K₄[Fe(CN)₆].

Ans [Fe(CN)6]⁴⁻

vi) In benzylic alcohols -OH group is bonded with …………….. hybridised carbon.

Ans sp²

vii) Glucose is converted to ethanol in presence of ……………………. enzyme.

Ans Zymase

viii) Sodium benzoate is used as ………………….

Ans Food Preservative

ix) Deficiency of vitamin…………………….. causes Beri-Beri disease.

Ans Vitamin B

x) The name of Sugar present in RNA is ……………….

Ans Ribose

3) Very short answer questions:

i) Define saturated solution.

Ans A saturated solution is a solution in which the maximum amount of solute has been dissolved at a given temperature, resulting in equilibrium between the dissolved and undissolved solute.

ii) Write names of solute and solvent present in sodium amalgam solution.

Ans Solute: Sodium (Na)

Solvent: Mercury (Hg)

iii) Rate K[A]^½[B]^½ Calculate the overall order of a reaction which has above rate expression.

Ans ½ + ½ = 1

So over all order – First order

iv) Write directive influence of -OCH₃ group present in anisole for electrophilic substitution reaction.

Ans: It directs incoming electrophiles to attack at ortho and para positions with respect to the methoxy (-OCH₃) group.

v) Write chemical name of white precipitate obtained on the reaction of phenol with bromine water.

Ans 2,4,6-tribromophenol.

vi) Write chemical name of NH₂-NHCONH₂

Ans Urea

vii) Write name of the product obtained from the reaction between benzenediazonium chloride and phenol.

Ans Coupling Reactions : Benzene diazonium chloride reacts with phenol in which the phenol molecule at its para position is coupled with the diazonium salt to form p-hydroxyazobenzene.

viii) Write isocyanide test for primary amines.

Ans Carbylamine reaction : Aliphatic and aromatic primary amines on heating with chloroform and ethanolic potassium hydroxide form isocyanides or carbylamines which are foul smelling substances. This reaction is known as carbylamines reaction or isocyanide test.

SECTION -B

Short answer type questions :

4) Calculate the mole fraction of gas A in the solution made on mixing 0.5 moles of gas A and 4.5 moles of gas B.

Ans To calculate the mole fraction of gas A in the solution, we need to first find the total number of moles in the solution, and then divide the moles of gas A by the total moles.

Given:

Moles of gas A = 0.5

Moles of gas B = 4.5

Total moles in the solution = Moles of gas A + Moles of gas B = 0.5 + 4.5 = 5 moles

Mole fraction of gas A = (Moles of gas A) / (Total moles)

= 0.5 / 5

= 0.1

So, the mole fraction of gas A in the solution is 0.1.

5) 0.05 moles of ethanoic acid is dissolved in 250g benzene. Calculate the molality of the solution.

Ans To calculate the molality of the solution, we use the formula:

Given:

Moles of ethanoic acid CH₃COOH = 0.05 moles-

Mass of benzene C₆H₆ = 250 g = 0.25 kg

Using the formula:

= 0.2 mol/kg

So, the molality of the solution is 0.2mol/kg.

6) Draw the Daniell cell.

Ans

7) Rate constant of a first order reaction is 1.386×10^-14 S^-1 calculate the half-life of the reaction.

Ans Half life of a first order reaction =

= = = S

8) Write any three physical characteristics of interstitial compounds.

Ans (i) They have high melting points in comparison to pure metals.

(ii) They are very hard.

(iii) They retain metallic conductivity.

9) Why transition metals exhibit catalytic properties? Explain.

Ans The catalytic activity of the transition elements can be explained by two basic facts.

(a) Owing to their ability to show variable oxidation states and form complexes,

transition metals form unstable intermediate compounds. Thus, they provide a new

path with lower activation energy, Ea, for the reaction.

(b) Transition metals also provide a suitable surface for the reactions to occur.

10) Despite being an electron withdrawing group why Cl-group is ortho-and para directing in electrophilic aromatic substitution? Give reason.

Ans The -I effect is stronger than the +R effect. This means overall, chlorine still deactivates the ring. However, the +R effect is enough to overcome the deactivating effect at the ortho and para positions. 

11) [A]

Ans

Write IUPAC name and chemical formula of [A] in the above reaction.

IUPAC Name of picric acid 2,4,6-trinitrophenol

12) Compound [x] is formed on heating ethanol with conc. H₂SO₄ at 413k temperature. Write IUPAC name of [x] and chemical equation of the reaction involved.

Ans

The IUPAC name of ethene is ethylene.

13)

Write chemical formula of [A] and [B] in above reaction sequence.

[A] [B]

14) Compare basic strength of aniline with ammonia.

Ans In gaseous phase, the order of basicity of amines is 3° amine > 2° amine > 1° amine > NH3.

15) Draw the double strand helix structure DNA.

SECTION -C

Long answer type questions :

16 i) Define order of reaction.

Ans Order of reaction : The sum of powers of the molar concentration of the reactants in the rate law expression is called the order of that chemical reaction. Order of reaction can be 0,1,2,3… and even a fraction.

Rate = k[A]^x [B]^y ⇒ Over all order of reaction n = x + y

ii) Explain pseudo first order reaction by giving appropriate example.

Ans Pseudo first order reaction : Such reaction whose order of reaction is one but molecularity are different then it is called as pseudo first order reaction.

eg. Inversion of cane sugar :

Rate ∝ [C₁₂H₂₂O₁₁]

order of reaction = 1 ⇒ Molecularity = 1 + 1 = 2

OR

i) Define molecularity of a reaction.

Ans Molecularity : The total number of molecules, atoms, ion taking part in the chemical reaction is known as molecularity of reaction. If one, two, three molecules take part in the reaction then the reaction are known as unimolecular, bimolecular, trimolecular respectively.

eg. H₂O₂ → H₂O + O₂ unimolecular

H₂ + I₂ → 2HI bimolecular

ii) Explain the role of activation energy in the feasibility of a chemical reaction.

Ans Lower the activation energy faster is the reaction.

17. Explain the geometry and the magnetic nature of complex [Co(NH₃)₆]³⁺ on the basis of valence bond theory.

Ans

Hybridisation – d²sp³

Structure – Octahedral (low spin)

Nature – Diamagnetic

OR

i) Write IUPAC name of an acid present in vinegar.

Ans Ethanoic acid.

ii) Explain the Rosenmund reduction by giving suitable chemical equation.

Rosenmund Reduction : Acyl chloride (acid chloride) is hydrogenated over catalyst, palladium on barium sulphate. This reaction is called Rosenmund reduction.

iii) [Z]

Write chemical formula of [Z] in above reaction.

Ans Benzaldehyde

SECTON – D

Essay type questions:

18) Explain-

i) The boiling points of isomeric heloalkanes decrease with increase in branching

ii) The melting point of p – isomer is higher than those of o – and m – isomers of isomeric dichlorobenzenes.

iii) The racemic mixture of a optically active compound is always optically inactive.

OR

Convert the following in single step (Write chemical equation only)

i) Benzenediazoniumchloride to iodobenzene.

ii) Chlorobenzene to diphenyl.

iii) Chloroethane to ethene

19) i) Describe the construction of standard hydrogen electrode.

ii) Write equations of cell reactions taking place at anode and cathode during use of dry cell.

OR

i) How does corrosion of iron occurs in presence of water and air? Describe.

ii) Write equations of cell reactions taking place at anode and cathode during use of mercury cell.

20) i)Write IUPAC name of an acid present in red-ant sting.

ii) Explain the Cannizzaro reaction by giving suitable chemical equation.

iii) CH₃COONa [A] + Na₂CO₃. Write chemical formula of [A] in above reaction.

OR

Explain the geometry and the magnetic nature of complex [CoF6]^3- on the basis of valence bond theory.