How can D₂O be prepared from water? Mention the physical properties in which D₂O differs from H₂O. Give at least three reactions of D₂O showing the exchange of hydrogen with deuterium.

<p><span data-teams="true">This is a long answer type question as classified in NCERT Exemplar</span></p><p>D₂O can be prepared by prolonged electrolysis of water. Due to high molecular mass D₂O differs from water.</p><p>NaOH+D₂O → NaOD+HOD</p><p>HCl+D₂O → DCl+ HOD</p><p>NH₄Cl+D₂O → NH₃DCl+HOD</p><p>Physical Properties of H₂O and D₂O</p><table><tbody><tr><td><p>Property&nbsp;</p></td><td><p>H₂O</p></td><td><p>D₂O</p></td></tr><tr><td><p>Molecular mass (g mol-1)</p></td><td><p>18.015</p></td><td><p>20.0276</p></td></tr><tr><td><p>Melting point/K&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</p></td><td><p>273.0&nbsp;&nbsp;</p></td><td><p>276.8</p></td></tr><tr><td><p>Boiling point/K&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</p></td><td><p>373.0&nbsp;&nbsp;</p></td><td><p>374.4</p></td></tr><tr><td><p>Enthalpy of formation/kJ mol^-1</p></td><td><p>-285.9&nbsp;</p></td><td><p>-294.6</p></td></tr><tr><td><p>Enthalpy of Vaporisation (373 K)/kJ mol^-1</p></td><td><p>40.66&nbsp;&nbsp;</p></td><td><p>41.61</p></td></tr><tr><td><p>Enthalpy of fusion/kJ mol^-1</p></td><td><p>6.01&nbsp;&nbsp;&nbsp;&nbsp;</p></td><td><p>—</p></td></tr><tr><td><p>Temp of max. density/K&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</p></td><td><p>276.98</p></td><td><p>284.2</p></td></tr><tr><td><p>Density (298 K)/g cm-3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</p></td><td><p>1.0000</p></td><td><p>1.1059</p></td></tr><tr><td><p>Viscosity/centipoise&nbsp;&nbsp;</p></td><td><p>0.8903</p></td><td><p>1.107</p></td></tr><tr><td><p>Dielectric constant</p></td><td><p>78.39&nbsp;&nbsp;</p></td><td><p>78.06</p></td></tr></tbody></table>

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