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Current Question (ID: 17929)

Question:
$\text{A given metal crystallizes out with a cubic structure having an edge length of } 361 \text{ pm. If there are four metal atoms in one unit cell, the radius of one atom is:}$
Options:
  • 1. $40 \text{ pm}$
  • 2. $127 \text{ pm}$
  • 3. $80 \text{ pm}$
  • 4. $108 \text{ pm}$
Solution:
$\text{Hint: To solve this numerical one must have the basic knowledge of the solid states.}$ $\text{When the metal crystallizes out with a cubic structure we need to determine the lattice first.}$ $\text{Once we come to know about the structure we can easily derive the relation between the radius and edge length of the atom.}$ $\text{Formula Used: The relation between the radius and edge length for FCC}$ $4r = \sqrt{2}a$ $\text{Where, } r \text{ is the radius of the atom,}$ $a \text{ is the edge length of the cubic structure.}$ $\text{Complete step by step answer:}$ $\text{First we will try to determine the lattice of a cubic structure.}$ $\text{For that we will read the question properly and we have given in the question that there are four metal atoms in one unit cell.}$ $\text{Therefore, } Z=4 \text{ where } Z \text{ represents the number of atoms in a unit cell.}$ $Z=4 \text{ is for the face centered cubic lattice (fcc).}$ $\text{Now we have determined the lattice of a cubic structure that is face centered cubic lattice.}$ $\text{So we will use the relation between radius and edge length for fcc.}$ $\text{We have, } a = 361 \text{ pm, we will substitute it in the relation of radius and edge length.}$ $4r = \sqrt{2}a - (1)$ $\text{Now substitute } a = 361 \text{ pm, in the above equation. we get,}$ $\Rightarrow 4r = \sqrt{2} \times 361 \text{ pm}$ $\Rightarrow r = \frac{\sqrt{2} \times 361}{4}$ $\Rightarrow r = 127.6 \text{ pm}$ $\text{From the above calculation, we get the radius of one atom as } r = 127.6 \text{ pm}$

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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
}