Class 12 Chemistry 2023 Board Exam

The colligative property used for the determination of molar mass of polymers and proteins is :
(a) Osmotic pressure
(b) Depression in freezing point
(c) Relative lowering in vapour pressure
(d) Elevation is boiling point

Which of the following is affected by catalyst ?
(a) ΔH
(b) ΔG
(c) Ea
(d) ΔS

The most common and stable oxidation state of a Lanthanoid is :
(a) + 2
(b) + 3
(c) + 4
(d) + 6

The synthesis of alkyl fluoride is best obtained from :
(a) Free radicals
(b) Swartz reaction
(c) Sandmeyer reaction
(d) Finkelstein reaction

When Benzene diazonium chloride reacts with phenol, it forms a dye. This reaction is called
(a) Diazotisation reaction
(b) Condensation reaction
(c) Coupling reaction
(d) Acetylation reaction

The correct cell to represent the following reaction is :
Zn + 2Ag⁺ → Zn²⁺ + 2Ag
(a) 2Ag | Ag⁺ || Zn | Zn²⁺
(b) Ag⁺ | Ag || Zn²⁺ | Zn
(c) Ag | Ag⁺ || Zn | Zn²⁺
(d) Zn | Zn²⁺ || Ag⁺ | Ag

The compounds [Co(SO₄)(NH₃)₅]Br and [Co(Br)(NH₃)₅]SO₄ represent :
(a) optical isomerism
(b) linkage isomerism
(c) ionisation isomerism
(d) coordination isomerism

The carbon–oxygen double bond is polarised in aldehydes and ketones due to higher electronegativity of oxygen relative to carbon. Therefore they undergo nucleophilic addition reactions with a number of nucleophiles such as HCN, NaHSO₃, alcohols, ammonia derivatives and Grignard reagents.

Aldehydes are easily oxidised by mild oxidising agents as compared to ketones. The carbonyl group of carboxylic acid does not give reactions of aldehydes and ketones. Carboxylic acids are considerably more acidic than alcohols and most of simple phenols.

Answer the following :

(a) Write the name of the product when an aldehyde reacts with excess alcohol in presence of dry HCl.

(b) Why carboxylic acid is a stronger acid than phenol ?

(c) (i) Arrange the following compounds in increasing order of their reactivity towards CH₃MgBr :
CH₃CHO, (CH₃)₃C – C(=O) – CH₃, CH₃ – C(=O) – CH₃
(ii) Write a chemical test to distinguish between propanal and propanone.

OR

(c) Write the main product in the following :
(i) [Cyclohexanone] + [Ag(NH₃)₂]⁺ →
(ii) [Benzaldehyde] + H₂NCONHNH₂ →

In the reaction R – OH + HCl $\stackrel{\text{ZnCl₂}}{\to }$ RCl + H₂O, what is the correct order of reactivity of alcohol ?
(a) 1° < 2° < 3°
(b) 1° > 3° > 2°
(c) 1° > 2° > 3°
(d) 3° > 1° > 2°

Which of the following does not give Cannizaro reaction ?
(a) (CH₃)₃ C – CHO
(b) (CH₃)₂ CH – CHO
(c) Benzaldehyde
(d) HCHO