CUET · CHEMISTRY · PYQ PAPER 2023

The aqueous solution containing which one of the following ions will be colourless? (Atomic numbers: \(Sc = 21, Fe = 26, Ti = 22, Mn = 25\))

A \(Sc^{3+}\)
B \(Fe^{2+}\)
C \(Ti^{3+}\)
D \(Mn^{2+}\)

Verified Solution

Answer & Solution

Correct Answer

(A) \(Sc^{3+}\)

Step-by-step Solution

Detailed explanation

Sc: \([Ar] 3d^1 4s^2\) \(Sc^{3+}\): \([Ar] 3d^0\) Colourless due to \(d^0\) configuration.

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 properties given in List-I with the metals given in List-II

List-I (Property)	List-II (Metal)
(A) 3d series element with highest melting point	(I) Os
(B) element which can show +8 oxidation state	(II) Fe
(C) 3d series element with largest number of oxidation states	(III) Cr
(D) constituent of Mischmetall	(IV) Mn

Choose the correct answer from the options given below:

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List - I (Complex)	List - II (Hybridisation)
(A) \([CoF_6]^{3-}\)	(I) \(sp^3\)
(B) \([Co(NH_3)_6]^{3+}\)	(II) \(dsp^2\)
(C) \([NiCl_4]^{2-}\)	(III) \(d^2sp^3\)
(D) \([Ni(CN)_4]^{2-}\)	(IV) \(sp^3d^2\)

List - I	List - II
(A) Urease	(I) Maltose
(B) Maltase	(II) Glucose and fructose
(C) Invertase	(III) \(NH _3\) and \(CO _2\)
(D) Diastase	(IV) Glucose