(C) : $\mathrm{CoCl}_{2}$ is a weak Lewis acids, reacting with chloride ion to produce salt containing the tetrahedral, and a deep magenta colour $\left[\mathrm{CoCl}_{4}\right]^{2-}$ ion. $\left[\mathrm{CoCl}_{4}\right]^{2-}$ is blue when anhydrous and a deep magenta colour when hydrated, therfore it is widely used as an indicator for water the reaction occurs as. $\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Cl}_{2}+2 \mathrm{HCl} \longrightarrow\left[\mathrm{CoCl}_{4}\right]^{2-}$ Pink solution Blue colour
AIIMS-2005
COORDINATION COMPOUNDS
274409
White silver surface turns black when $\mathrm{O}_{3}$ is passed over it. This is due to the formaton of
1 silver hydroxide.
2 freshly reduced silver which is black in colour.
(A) d-d transition is a process of shifting of electrons between the lower energy d-orbital to a higher energy d-orbital by absorption of energy, So the colour is due to charge transfer not due to d-d transition. Here, in $\mathrm{CrO}_{4}^{2-} \mathrm{Cr}$ is in +6 oxidation state which has $\mathrm{d}^{0}$ configuration.
UP CPMT-2013
COORDINATION COMPOUNDS
274420
Which compound is expected to be coloured ?
1 $\mathrm{CaCl}$
2 $\mathrm{CuF}_{2}$
3 $\mathrm{Ag}_{2} \mathrm{SO}_{4}$
4 $\mathrm{MgF}_{2}$
Explanation:
(B) : The compound of transition metals show colours mainly due to electronic transition between partially filled d-orbitals. In $\mathrm{CuF}_{2}, \mathrm{Cu}$ is present as $\mathrm{Cu}^{2+}$. $\mathrm{Cu}^{2+}=[\mathrm{Ar}] 3 \mathrm{~d}^{9}, 4 \mathrm{~s}^{0}$ Since, in it one unpaired electron is present, it is coloured.
(C) : $\mathrm{CoCl}_{2}$ is a weak Lewis acids, reacting with chloride ion to produce salt containing the tetrahedral, and a deep magenta colour $\left[\mathrm{CoCl}_{4}\right]^{2-}$ ion. $\left[\mathrm{CoCl}_{4}\right]^{2-}$ is blue when anhydrous and a deep magenta colour when hydrated, therfore it is widely used as an indicator for water the reaction occurs as. $\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Cl}_{2}+2 \mathrm{HCl} \longrightarrow\left[\mathrm{CoCl}_{4}\right]^{2-}$ Pink solution Blue colour
AIIMS-2005
COORDINATION COMPOUNDS
274409
White silver surface turns black when $\mathrm{O}_{3}$ is passed over it. This is due to the formaton of
1 silver hydroxide.
2 freshly reduced silver which is black in colour.
(A) d-d transition is a process of shifting of electrons between the lower energy d-orbital to a higher energy d-orbital by absorption of energy, So the colour is due to charge transfer not due to d-d transition. Here, in $\mathrm{CrO}_{4}^{2-} \mathrm{Cr}$ is in +6 oxidation state which has $\mathrm{d}^{0}$ configuration.
UP CPMT-2013
COORDINATION COMPOUNDS
274420
Which compound is expected to be coloured ?
1 $\mathrm{CaCl}$
2 $\mathrm{CuF}_{2}$
3 $\mathrm{Ag}_{2} \mathrm{SO}_{4}$
4 $\mathrm{MgF}_{2}$
Explanation:
(B) : The compound of transition metals show colours mainly due to electronic transition between partially filled d-orbitals. In $\mathrm{CuF}_{2}, \mathrm{Cu}$ is present as $\mathrm{Cu}^{2+}$. $\mathrm{Cu}^{2+}=[\mathrm{Ar}] 3 \mathrm{~d}^{9}, 4 \mathrm{~s}^{0}$ Since, in it one unpaired electron is present, it is coloured.
(C) : $\mathrm{CoCl}_{2}$ is a weak Lewis acids, reacting with chloride ion to produce salt containing the tetrahedral, and a deep magenta colour $\left[\mathrm{CoCl}_{4}\right]^{2-}$ ion. $\left[\mathrm{CoCl}_{4}\right]^{2-}$ is blue when anhydrous and a deep magenta colour when hydrated, therfore it is widely used as an indicator for water the reaction occurs as. $\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Cl}_{2}+2 \mathrm{HCl} \longrightarrow\left[\mathrm{CoCl}_{4}\right]^{2-}$ Pink solution Blue colour
AIIMS-2005
COORDINATION COMPOUNDS
274409
White silver surface turns black when $\mathrm{O}_{3}$ is passed over it. This is due to the formaton of
1 silver hydroxide.
2 freshly reduced silver which is black in colour.
(A) d-d transition is a process of shifting of electrons between the lower energy d-orbital to a higher energy d-orbital by absorption of energy, So the colour is due to charge transfer not due to d-d transition. Here, in $\mathrm{CrO}_{4}^{2-} \mathrm{Cr}$ is in +6 oxidation state which has $\mathrm{d}^{0}$ configuration.
UP CPMT-2013
COORDINATION COMPOUNDS
274420
Which compound is expected to be coloured ?
1 $\mathrm{CaCl}$
2 $\mathrm{CuF}_{2}$
3 $\mathrm{Ag}_{2} \mathrm{SO}_{4}$
4 $\mathrm{MgF}_{2}$
Explanation:
(B) : The compound of transition metals show colours mainly due to electronic transition between partially filled d-orbitals. In $\mathrm{CuF}_{2}, \mathrm{Cu}$ is present as $\mathrm{Cu}^{2+}$. $\mathrm{Cu}^{2+}=[\mathrm{Ar}] 3 \mathrm{~d}^{9}, 4 \mathrm{~s}^{0}$ Since, in it one unpaired electron is present, it is coloured.
(C) : $\mathrm{CoCl}_{2}$ is a weak Lewis acids, reacting with chloride ion to produce salt containing the tetrahedral, and a deep magenta colour $\left[\mathrm{CoCl}_{4}\right]^{2-}$ ion. $\left[\mathrm{CoCl}_{4}\right]^{2-}$ is blue when anhydrous and a deep magenta colour when hydrated, therfore it is widely used as an indicator for water the reaction occurs as. $\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Cl}_{2}+2 \mathrm{HCl} \longrightarrow\left[\mathrm{CoCl}_{4}\right]^{2-}$ Pink solution Blue colour
AIIMS-2005
COORDINATION COMPOUNDS
274409
White silver surface turns black when $\mathrm{O}_{3}$ is passed over it. This is due to the formaton of
1 silver hydroxide.
2 freshly reduced silver which is black in colour.
(A) d-d transition is a process of shifting of electrons between the lower energy d-orbital to a higher energy d-orbital by absorption of energy, So the colour is due to charge transfer not due to d-d transition. Here, in $\mathrm{CrO}_{4}^{2-} \mathrm{Cr}$ is in +6 oxidation state which has $\mathrm{d}^{0}$ configuration.
UP CPMT-2013
COORDINATION COMPOUNDS
274420
Which compound is expected to be coloured ?
1 $\mathrm{CaCl}$
2 $\mathrm{CuF}_{2}$
3 $\mathrm{Ag}_{2} \mathrm{SO}_{4}$
4 $\mathrm{MgF}_{2}$
Explanation:
(B) : The compound of transition metals show colours mainly due to electronic transition between partially filled d-orbitals. In $\mathrm{CuF}_{2}, \mathrm{Cu}$ is present as $\mathrm{Cu}^{2+}$. $\mathrm{Cu}^{2+}=[\mathrm{Ar}] 3 \mathrm{~d}^{9}, 4 \mathrm{~s}^{0}$ Since, in it one unpaired electron is present, it is coloured.
