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Current Question (ID: 10973)

Question:

$\text{The Lassaigne's extract is boiled with conc. HNO}_3 \text{ while testing for halogens, because it:}$

Options:

1. $\text{Helps in the precipitation of AgCl}$
2. $\text{Increases the solubility product of AgCl}$
3. $\text{Increases the concentration of NO}_3^- \text{ ions}$
4. $\text{Decomposes Na}_2\text{S and NaCN, if formed}$ (Correct)

Solution:

$\text{Hint: Lassaigne's test}$ $\text{Explanation:}$ $\text{Na}_2\text{S and NaCN, if present in the extract, will be decomposed to H}_2\text{S and HCN by HNO}_3$ $\text{NaCN} + \text{HNO}_3 \rightarrow \text{NaNO}_3 + \text{HCN}$ $\text{Na}_2\text{S} + 2\text{HNO}_3 \rightarrow 2\text{NaNO}_3 + \text{H}_2\text{S}$ $\text{These will escape from the solution and will not interfere with the test for halogens.}$

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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
}