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Current Question (ID: 18496)

Question:

$\text{Incorrect statement for the Hall-Heroult process is:}$

Options:

1. $\text{Cryolite } \text{Na}_3\text{AlF}_6 \text{ lower the melting point of } \text{Al}_2\text{O}_3, \text{ and increase its electrical conductivity.}$
2. $\text{Al is obtained at the cathode, and CO}_2 \text{ at the anode.}$
3. $\text{Li}_2\text{CO}_3 \text{ can be used in place of cryolite(}\text{Na}_3\text{AlF}_6\text{)}$
4. $\text{MgF}_2 \text{ can be used in place of fluorspar (CaF}_2\text{)}$

Solution:

$\text{HINT: MgF}_2 \text{ can't be used in place of fluorspar (CaF}_2\text{)}$ $\text{Explanation:}$ $\text{STEP 1:}$ $\text{Carbon anode is oxidised to CO and CO}_2\text{. When Al}_2\text{O}_3 \text{ is mixed with CaF}_2\text{, it lowers the melting point of the mixture and brings conductivity.}$ $\text{Al}^{+3} \text{ is reduced at the cathode to form Al.}$ $\text{The reactions involved are:}$ $1. \text{Al}^{+3} + 3 \text{e}^- \rightarrow \text{Al (l)} \text{ (at the cathode)}$ $2. \text{At anode:}$ $\text{C(s)} + \text{O}^{2-} \rightarrow \text{CO (g)} + 2\text{e}^-$ $\text{C(s)} + 2\text{O}^{2-} \rightarrow \text{CO}_2\text{(g)} + 4\text{e}^-$ $\text{STEP 2:}$ $\text{Mg}^{+2} \text{ cation will be preferentially discharged than Al}^{+3} \text{ at the cathode. So, MgF}_2 \text{ cannot be used in place of fluorspar (CaF}_2\text{)}$ $\text{Lithium carbonate also plays a key role in the production of Aluminium metal.}$ $\text{In this process, the chemical reduces the temperature to extract pure Li from bauxite ore.}$

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Upload a JSON file containing LaTeX/MathJax formatted question, options, and solution.

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
}