CUET · CHEMISTRY · PYQ PAPER 2023

Which of the following reactions has a positive \(\Delta S^{\circ}\) value?

A \(6FeO(s) + O_2(g) \rightarrow 2Fe_3O_4(s)\)
B \(2C(s) + O_2(g) \rightarrow 2CO(g)\)
C \(4Al(s) + 3O_2(g) \rightarrow 2Al_2O_3(s)\)
D \(2CO(g) + O_2(g) \rightarrow 2CO_2(g)\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(2C(s) + O_2(g) \rightarrow 2CO(g)\)

Step-by-step Solution

Detailed explanation

\(2C(s) + O_2(g) \rightarrow 2CO(g)\) \(\Delta n_{gas} = 2 - 1 = +1\) Since \(\Delta n_{gas} > 0\), \(\Delta S^{\circ} > 0\).

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Match the catalysts given in List - I with the process catalyzed by them given in List - II

List - I (Catalyst)	List - II (Process)
(A) Ni in presence of Hydrogen	(I) Ziegler Natta Catalyst
(B) Finely divided iron	(II) Vegetable oil to ghee
(C) \(TiCl _4+ Al \left( CH _3\right)_3\)	(III) Sandmeyer reaction
(D) \(Cu _2 Cl _2\)	(IV) Haber's process

Choose the correct answer from the options given below:

CUET 2025 Easy

Match List-l with List-ll

List-I (Name of the molecule/drug)	List-II (Use/disease name)
(A) Thyroxine	(I) Scurvy
(B) Ascorbic acid	(II) Thyroid gland
(C) Steroid hormones	(III) Identification of criminals
(D) DNA fingerprinting	(IV) Adrenal cortex

Choose the correct answer from the options given below:

CUET 2025 Medium

The conductivity of 0.001 mol \(\text{L}^{-1}\) acetic acid is \(5.01 \times 10^{-5} \text{ S cm}^{-1}\).
Calculate its dissociation constant if \(\Lambda_m^{\circ}\) for acetic acid is
390.5 \(\text{S cm}^2 \text{mol}^{-1}\).

CUET 2023 Medium

Match List-l with List-II

List-l (Test)	List-II (Identification)
(A) Hinsberg's Test	(I) Primary, Secondary and tertiary Amines
(B) Isocyanide test	(II) Aliphatic and Aromatic primary amines
(C) Azo dye test	(III) Primary Aromatic amines
(D) Tollen's Test	(IV) Reducing sugars

Choose the correct answer from the options given below:

CUET 2025 Hard

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