Medium MCQ +4 / -1 PYQ · JEE Mains 2020

Complex A has a composition of H12O6Cl3Cr. If the complex on treatment with conc.H2SO4 loses 13.5% of its original mass, the correct molecular formula of A is :
[Given: atomic mass of Cr = 52 amu and Cl = 35 amu]

  1. A [Cr(H<sub>2</sub>O)<sub>5</sub>Cl]Cl<sub>2</sub>.H<sub>2</sub>O
  2. B [Cr(H<sub>2</sub>O)<sub>4</sub>Cl<sub>2</sub>]Cl.2H<sub>2</sub>O Correct answer
  3. C [Cr(H<sub>2</sub>O)<sub>3</sub>Cl<sub>3</sub>].3H<sub>2</sub>O
  4. D [Cr(H<sub>2</sub>O)<sub>6</sub>]Cl<sub>3</sub>

Solution

Let x molecule of water are lost then <br><br>13.5 = $$\left[ {{{x \times 18} \over {6 \times 18 + 3 \times 35 + 52}}} \right] \times 100$$ <br><br>$\Rightarrow$ x = 1.99 $\simeq$ 2 <br><br>$\therefore$ Around two moles of water are lost during heating. <br><br>$\therefore$ Formula of complex could be <br><br> [Cr(H<sub>2</sub>O)<sub>4</sub>Cl<sub>2</sub>]Cl.2H<sub>2</sub>O

About this question

Subject: Chemistry · Chapter: Coordination Compounds · Topic: Ligands and Coordination Number

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