Import Question JSON

Current Question (ID: 21224)

Question:

$\text{Which of the following compounds is added to the sodium extract before the addition of silver nitrate for testing of halogens?}$

Options:

1. $\text{Nitric acid}$
2. $\text{Ammonia}$
3. $\text{Hydrochloric acid}$
4. $\text{Sodium hydroxide}$

Solution:

$\text{Hint: Nitric acid destroys NaCN and } \text{Na}_2\text{S}$ $\text{In the testing of halogens (Cl}^-, \text{Br}^-, \text{and I}^-) \text{in an organic compound using the Lassaigne's test, nitric acid (HNO}_3) \text{is added to the sodium extract (also called Lassaigne's extract) before testing with silver nitrate (AgNO}_3). \text{This is done to eliminate interfering ions such as cyanide (CN}^-) \text{or sulfide (S}^{2-}), \text{which can also form precipitates with silver nitrate.}$ $\text{Both CN}^- \text{and S}^{2-} \text{can form precipitates with Ag}^+, \text{interfering with the detection of halides.}$ $\text{Ag}^+ + \text{CN}^- \rightarrow \text{AgCN (white precipitate)}$ $\text{Ag}^+ + \text{S}^{2-} \rightarrow \text{Ag}_2\text{S (black precipitate)}$ $\text{To prevent this, nitric acid is added, which reacts with CN}^- \text{and S}^{2-} \text{to form HCN (hydrocyanic acid) and H}_2\text{S (hydrogen sulfide), respectively. These are volatile and escape as gases.}$ $\text{So, option 1 is the correct answer.}$

Import JSON File

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
}