JEE Main 2018 — Chemistry Inorganic Chemistry

2018mcqmedium

The incorrect statement is:

Official previous-year question

Held on 16 Apr 2018 · Verified 6 Jul 2026.

Options

A
${\mathrm{Cu}}^{2+}$ ion gives chocolate coloured precipitate with potassium ferrocyanide solution
B
${\mathrm{Cu}}^{2+} \mathrm{and} {\mathrm{Ni}}^{2+}$ ions give black precipitate with ${H}_{2}S$ in presence of HCl solution
C
Ferric ion gives blood red colour with potassium thiocyanate
D
${\mathrm{Cu}}^{2+}$ salts give red coloured borax bead test in reducing flame

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Solution

Cu $^{+2}$ gives black precipitate in presence of dil. HCl Ni $^{+2}$ ions gives black precipitate in presence of NH $_{4}$ Cl +NH $_{3}$

with HCl S $^{2-}$ concentration is not just sufficient to overcome the solubility product of NiS.

${\mathrm{Cu}}^{+2}+{H}_{2}S\overset{\mathrm{dil}.\mathrm{HCl}}{\rightarrow }\underset{(\mathrm{black})}{{\mathrm{Cu}}_{2}S\downarrow }+2{H}^{+}$

${\mathrm{Ni}}^{+2}+{H}_{2}S\rightarrow _{{\mathrm{NH}}_{4}\mathrm{Cl}}^{{\mathrm{NH}}_{4}\mathrm{OH}}\underset{(\mathrm{black})}{\mathrm{NiS}\downarrow }+2{H}^{+}$

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JEE Main 2018 — Chemistry Inorganic Chemistry

2018mcqmedium

The incorrect statement is:

Official previous-year question

Held on 16 Apr 2018 · Verified 6 Jul 2026.

Options

A
${\mathrm{Cu}}^{2+}$ ion gives chocolate coloured precipitate with potassium ferrocyanide solution
B
${\mathrm{Cu}}^{2+} \mathrm{and} {\mathrm{Ni}}^{2+}$ ions give black precipitate with ${H}_{2}S$ in presence of HCl solution
C
Ferric ion gives blood red colour with potassium thiocyanate
D
${\mathrm{Cu}}^{2+}$ salts give red coloured borax bead test in reducing flame

Did you get this right?

Solution

Cu $^{+2}$ gives black precipitate in presence of dil. HCl Ni $^{+2}$ ions gives black precipitate in presence of NH $_{4}$ Cl +NH $_{3}$

with HCl S $^{2-}$ concentration is not just sufficient to overcome the solubility product of NiS.

${\mathrm{Cu}}^{+2}+{H}_{2}S\overset{\mathrm{dil}.\mathrm{HCl}}{\rightarrow }\underset{(\mathrm{black})}{{\mathrm{Cu}}_{2}S\downarrow }+2{H}^{+}$

${\mathrm{Ni}}^{+2}+{H}_{2}S\rightarrow _{{\mathrm{NH}}_{4}\mathrm{Cl}}^{{\mathrm{NH}}_{4}\mathrm{OH}}\underset{(\mathrm{black})}{\mathrm{NiS}\downarrow }+2{H}^{+}$

JEE Main 2018 — Chemistry Inorganic Chemistry

Options

Did you get this right?

Solution

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JEE Main Inorganic Chemistry in other years

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Physical Chemistry

Organic Chemistry

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JEE Main 2018 — Chemistry Inorganic Chemistry

Options

Did you get this right?

Solution

Your note

JEE Main Inorganic Chemistry in other years

More JEE Main Inorganic Chemistry questions

Other Chemistry topics for JEE Main

Physical Chemistry

Organic Chemistry

Keep practicing Inorganic Chemistry