In which of the following hydride law of constant composition does not hold good.

detailed solution

Correct option is D

Interstitial hydrides [Transition metal hydrides] are non-stoichiometric hydrides. They do not follow the valency rules. The formula of non stoichiometric hydrides do not corresponds to any of the oxidation state of metal.Zr H1.3 - 1.75 ⇒ Non - stoichiometric hydridesZr H⇒ [Kr] 4d2 5s2 ⇒ Zr+ H- ⇒ ZrH                               Zr+2 +2H- ⇒ ZrH2                               Zr+3 + 3H- ⇒ ZrH3                               Zr+4 + 4H- ⇒ ZrH4The formula of Zirconium hydride should be either ZrH, (or) ZrH2, (or) ZrH3, (or) ZrH4, but its formula is Zr H1.3 - 1.75, i.e., it does not follow the valency neles