Import Question JSON

Current Question (ID: 8391)

Question:

$\text{When hydrochloric acid is added to cobalt nitrate solution at room temperature, the following reaction takes place and the reaction mixture becomes blue. On cooling the mixture it becomes pink}$ $[\text{Co}(\text{H}_2\text{O})_6]^{3+}\text{(aq)} + 4\text{Cl}^-\text{(aq)} \rightleftharpoons [\text{CoCl}_4]^{2-}\text{(aq)} + 6\text{H}_2\text{O}\text{(l)}$ $\text{(Pink)} \qquad\qquad\qquad\qquad\qquad\qquad \text{(Blue)}$ $\text{On the basis of the information given above, mark the correct answer:}$

Options:

1. $\Delta H > 0 \text{ for the reaction}$
2. $\Delta H < 0 \text{ for the reaction}$
3. $\Delta H = 0 \text{ for the reaction}$
4. $\text{The sign of } \Delta H \text{ cannot be predicted on the basis of the given information.}$

Solution:

$\text{Hint: For endothermic reaction, equilibrium shifts in forward direction on heating.}$ $\text{Explanation:}$ $\text{In this reaction,}$ $[\text{Co}(\text{H}_2\text{O})_6]^{3+}\text{(aq)} + 4\text{Cl}^-\text{(aq)} \rightleftharpoons [\text{CoCl}_4]^{2-}\text{(aq)} + 6\text{H}_2\text{O}\text{(l)}$ $\text{(Pink)} \qquad\qquad\qquad\qquad\qquad\qquad \text{(Blue)}$ $\text{On cooling, the equilibrium shifts backward direction or on heating, the equilibrium shifts toward forward direction. Hence, reaction is endothermic, i.e., } \Delta H > 0.$ $\text{Analysis of the observations:}$ $\text{• At room temperature: Mixture becomes blue (forward reaction favored)}$ $\text{• On cooling: Mixture becomes pink (backward reaction favored)}$ $\text{• This implies: Heating favors forward reaction, cooling favors backward reaction}$ $\text{According to Le Chatelier's Principle:}$ $\text{• If heating favors the forward reaction, then the forward reaction must be endothermic}$ $\text{• Endothermic reactions have } \Delta H > 0$ $\text{• When heat is added, the system shifts to consume the heat (forward direction)}$ $\text{• When heat is removed (cooling), the system shifts to produce heat (backward direction)}$ $\text{Therefore, } \Delta H > 0 \text{ for this reaction.}$

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
}