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Current Question (ID: 18759)

Question:

$\text{A pair that contains both the ions coloured in an aqueous solution is:}$ $\text{(At. no. : Sc = 21, Ti = 22, Ni = 28, Cu = 29, Co = 27)}$

Options:

1. $\text{Ni}^{2+}, \text{Ti}^{3+}$
2. $\text{Sc}^{3+}, \text{Ti}^{3+}$
3. $\text{Sc}^{3+}, \text{Co}^{2+}$
4. $\text{Ni}^{2+}, \text{Cu}^{+}$

Solution:

$\text{HINT: Any transition metal ion which has one or more unpaired electrons is colored due to their tendency to show d-d transition.}$ $\text{Explanation:}$ $\text{This can be found out from their electronic configurations.}$ $1.\ 28\text{Ni}=1s^2 2s^2 2p^6 3s^2 3p^6 3d^8 4s^2$ $\text{Ni}^{2+} = 1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^8$ $\text{(unpaired)}$ $2.\ 22\text{Ti} = 1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^2 4s^2$ $\text{Ti}^{3+} = 1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^1$ $\text{(unpaired)}$ $3.\ 21\text{Sc} = 1s^2 2s^2 2p^6 3s^2 3p^6 3d^1 4s^2$ $\text{Sc}^{3+} = 1s^2 2s^2 2p^6 3s^2 3p^6$ $\text{(electrons absent in d-orbitals)}$ $4.\ 29\text{Cu} = 1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^{10} 4s^1$ $\text{Cu}^{+} = 1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^{10}$ $\text{(Complete d-orbital or no unpaired electrons in d orbital)}$ $\text{Hence, } \text{Ni}^{2+} \text{ and } \text{Ti}^{3+} \text{ ions are coloured.}$

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Expected JSON Format:

{
  "question": "The mass of carbon present in 0.5 mole of $\\mathrm{K}_4[\\mathrm{Fe(CN)}_6]$ is:",
  "options": [
    {
      "id": 1,
      "text": "1.8 g"
    },
    {
      "id": 2,
      "text": "18 g"
    },
    {
      "id": 3,
      "text": "3.6 g"
    },
    {
      "id": 4,
      "text": "36 g"
    }
  ],
  "solution": "\\begin{align}\n&\\text{Hint: Mole concept}\\\\\n&1 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\text{ moles of carbon atom}\\\\\n&0.5 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\times 0.5 \\text{ mol} = 3 \\text{ mol}\\\\\n&1 \\text{ mol of carbon} = 12 \\text{ g}\\\\\n&3 \\text{ mol carbon} = 12 \\times 3 = 36 \\text{ g}\\\\\n&\\text{Hence, 36 g mass of carbon present in 0.5 mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6].\n\\end{align}",
  "correct_answer": 4
}