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Current Question (ID: 21528)

Question:

$\text{If dichromate ion is treated with base, the oxidation number of Cr in the product formed will be:}$

Options:

1. $+6$
2. $+4$
3. $+5$
4. $+2$

Solution:

$\text{Hint: The molecular formula of the product is } \text{K}_2\text{CrO}_4.$ $\text{Step 1:}$ $\text{On heating with alkalies, it is converted to chromate, i.e., the colour changes from orange to yellow. On acidifying, the yellow colour again changes to orange.}$ $\text{The reaction is as follows:}$ $\text{K}_2\text{Cr}_2\text{O}_7 + 2\text{KOH} \rightarrow 2\text{K}_2\text{CrO}_4 + \text{H}_2\text{O}$ $\text{Step 2:}$ $\text{The product is } \text{K}_2\text{CrO}_4. \text{ Calculate the oxidation state of Cr in } \text{K}_2\text{CrO}_4 \text{ as follows:}$ $\text{Let the oxidation state of Cr is } x:$ $2(1) + x + (-2 \times 4) = 0$ $2 + x - 8 = 0$ $x = +6$

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
}