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Current Question (ID: 7960)

Question:

$\text{Lewis symbols for the atoms and ions: S and S}^{2-}\text{; Al and Al}^{3+}\text{; H and H}^-\text{ respectively, would be:}$

Options:

1. $\text{S with 6 dots around it; [S with 8 dots around it]}^{2-}\text{; Al}^{3+}\text{; Al with 1 dot; H with 1 dot; [H with 2 dots]}^-$ (Correct)
2. $\text{S with 6 dots around it; [S with 8 dots around it]}^{2-}\text{; Al with 1 dot; Al}^{3+}\text{; H with 1 dot; [H with 2 dots]}^-$
3. $\text{[S with 8 dots around it]}^{2-}\text{; S with 6 dots around it; Al with 1 dot; Al}^{3+}\text{; H with 1 dot; [H with 2 dots]}^-$
4. $\text{S with 6 dots around it; [S with 8 dots around it]}^{2-}\text{; Al with 1 dot; Al}^{3+}\text{; [H with 2 dots]}^-\text{; H with 1 dot}$

Solution:

$\text{HINT: It is a simple notation to represent valence electrons in an atom.}$\n\n$\text{Explanation:}$\n\n$\text{(i) S and S}^{2-}$\n\n$\text{The number of valence electrons in sulphur is 6.}$\n\n$\text{The Lewis dot symbol of sulphur (S) is } \cdot\text{S}\cdot\text{.}$\n\n$\text{The di-negative charge infers that there will be two electrons more in addition to the six valence electrons. Hence, the Lewis dot symbol of S}^{2-}\text{ is [}\cdot\text{S}\cdot\text{]}^{2-}\text{.}$\n\n$\text{(ii) Al and Al}^{3+}$\n\n$\text{The number of valence electrons in aluminium is 3.}$\n\n$\text{The Lewis dot symbol of aluminium (Al) is } \cdot\text{Al}\cdot\text{.}$\n\n$\text{The tri-positive charge on a species infers that it has donated its three electrons. Hence, the Lewis dot symbol is [Al]}^{3+}\text{.}$\n\n$\text{(iii) H and H}^-$\n\n$\text{The number of valence electrons in hydrogen is 1.}$\n\n$\text{The Lewis dot symbol of hydrogen (H) is H}\cdot\text{.}$\n\n$\text{The uni-negative charge infers that there will be one electron more in addition to the one valence electron. Hence, the Lewis dot symbol is [H}\cdot\text{]}^-\text{.}$

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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
}