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Chemistry · 2025 · 5 marks
CBSE 2025 · Region 2 · Set 1 · Q33
(A) An organic compound 'A', molecular formula C_2 H_6 O oxidises with CrO_3 to form a compound 'B'. Compound 'B' on warming with iodine and aqueous…
(A)
An organic compound 'A', molecular formula $\displaystyle \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ oxidises with $\displaystyle \mathrm{CrO}_{3}$ to form a compound 'B'. Compound 'B' on warming with iodine and aqueous solution of NaOH gives a yellow precipitate of compound 'C'. When compound 'A' is heated with conc. $\displaystyle \mathrm{H}_{2} \mathrm{SO}_{4}$ at $\displaystyle 413$ K gives a compound 'D', which on reaction with excess HI gives compound 'E'. Identify compounds 'A', 'B', 'C', 'D' and 'E' and write chemical equations involved.
OR 33. (B) (a) Write chemical equations of the following reactions : $\displaystyle \mathbf{3}+\mathbf{1}+\mathbf{1}=\mathbf{5}$
(i)
Phenol is treated with conc. $\displaystyle \mathrm{HNO}_{3}$
(ii)
Propene is treated with $\displaystyle \mathrm{B}_{2} \mathrm{H}_{6}$ followed by oxidation by $\displaystyle \mathrm{H}_{2} \mathrm{O}_{2} / \mathrm{OH}^{-}$.
(iii)
Sodium t-butoxide is treated with $\displaystyle \mathrm{CH}_{3} \mathrm{Cl}$.
(b)
Give a simple chemical test to distinguish between butan-$\displaystyle 1$-ol and butan-$\displaystyle 2$-ol.
(c)
Arrange the following in increasing order of acid strength : phenol, ethanol, water
Marking-scheme solution
A = CH3CH2OH / Ethanol / Ethyl alcohol,
B = CH3CHO / Ethanal / Acetaldehyde,
C = CHI3 / Iodoform / Triiodomethane,
D = CH3CH2O CH2 CH3 / Ethoxyethane / Diethyl ether,
E = CH3CH2I / Ethyl iodide / Iodoethane.
(a)
(i)
(ii)
(iii)
(b)
On heating with NaOH + I2, Butan-$\displaystyle 2$-ol gives yellow ppt. Of iodoform (CHI3 ) whereas Butan-$\displaystyle 1$-
ol does not.
(c)
Ethanol < Water < Phenol.
All Alcohols, Phenols and Ethers questions2025 question paperNCERT solutions: Alcohols, Phenols and EthersPractice Alcohols, Phenols and Ethers →
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CBSE Class 12 Chemistry past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.