Table: Formulation of Cobalt(III) Chloride-Ammonia Complexes Colour Formula Solution conductivity corresponds to --- --- --- Yellow [Co(NH_3)_6]³+3Cl^- Y Purple [CoCl(NH_3)_5]²+2Cl^- 1:2 electrolyte Green X 1:1 electrolyte 'X' and 'Y' in the above table are: (A) X=[Co(NH_3)_6]²+3Cl^-, Y= 1:3 (B) X= [Co(NH_3)_4Cl_2]^+Cl^-, Y= 1:3 (C) X=[Co(NH_3)_4Cl_2]^+Cl^-, Y= 1:1 (D) X=[Co(NH_3)_4Cl_2]³+3Cl^-, Y= 1:1

ChemistryCBSE Class 12 · Sample paper, session 2024-25 · 1 mark · MCQ

CBSE Class 12 Chemistry sample paper 2024-25: question 7

From the official CBSE sample question paper for 2024-25, section A, question 7, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q7 · 1 mark · MCQCoordination Compounds

Table: Formulation of Cobalt(III) Chloride-Ammonia Complexes

Colour	Formula	Solution conductivity corresponds to
Yellow	$[C o (N H_{3})_{6}]^{3 +} 3 C l^{-}$	Y
Purple	$[C o C l (N H_{3})_{5}]^{2 +} 2 C l^{-}$	1:2 electrolyte
Green	X	1:1 electrolyte

'X' and 'Y' in the above table are:

(A)X= $[C o (N H_{3})_{6}]^{2 +} 3 C l^{-}$ , Y= 1:3
(B)X= $[C o (N H_{3})_{4} C l_{2}]^{+} C l^{-}$ , Y= 1:3
(C)X= $[C o (N H_{3})_{4} C l_{2}]^{+} C l^{-}$ , Y= 1:1
(D)X= $[C o (N H_{3})_{4} C l_{2}]^{3 +} 3 C l^{-}$ , Y= 1:1

Figure in the paper: Table of cobalt(III) chloride-ammonia complexes with colour, formula and conductivity type; X and Y are blanks to be identified (reproduced in stem). See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

Open one hint at a time and try again before the next.

Hint 1

Count the ions each complex gives in solution.

Hint 2

Chlorides inside the coordination sphere do not ionise.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

$[Co (N H_{3})_{6}] C l_{3}$ gives 1 complex cation and 3 Cl $^{-}$ ions, so Y = 1:3 electrolyte.
A 1:1 electrolyte has only one ionisable Cl $^{-}$ , so X = $[Co (N H_{3})_{4} C l_{2}]^{+} C l^{-}$ . Option (B).
1 mark

Answer: Option (B)

Where the marks are

Identifies X and Y from the number of ionisable chlorides (1 mark)

Revise the chapter

Chapter: Coordination Compounds (notes, formulas, where marks are lost and every past question)

Practise this chapterBoard-style questions from Coordination Compounds, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2024-25: every question, by section.

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CBSE Class 12 Chemistry sample paper 2024-25: question 7

Hints

Step-by-step solution

Revise the chapter

More questions from Coordination Compounds