Q.The reaction H₃PO₂ + D₂O → H₂DPO₂ + HDO indicates that hypo-phosphorus acid is

Heavy water, $D_2O$, is the deuterium analogue of ordinary water and is chemically very similar to $H_2O$, since it undergoes essentially the same types of reactions (bent structure, hydrogen bonding through O–D, amphoteric behaviour) governed by the same electron configuration of oxygen. However, its physical properties differ noticeably because deuterium is roughly twice as massive as protium: $D_2O$ has a higher boiling point (about $101.4^\circ C$ versus $100^\circ C$), a higher melting point, greater density, and greater viscosity than ordinary water. It is manufactured by the prolonged electrolysis of ordinary water, because the lighter $H_2O$ molecules are preferentially decomposed at the electrodes, leaving the residual water progressively enriched in $D_2O$. Despite its chemical similarity to ordinary water, $D_2O$ is not considered suitable for regular dri …