1.878 g of MBrx  when heated in a stream of HCl gas was completely converted into chloride, MClx  which weighed 1.0 g. The specific heat of metal is 0.14 cal g-1. The molecular weight of the metal bromide is

MBrx+xHCl→HClx+xHBr⇒1.878EM+80x=1EM+35.5x⇒(1.878)EM+35.5x=EM+80x                                              ⇒0.878 EM=80−35.5×1.878⇒ EM=13.33/0.878=15.18\ Atomic weight × specific heat = 6.4 ( Dulong petits law)⇒ Atomic weight (Approximate) =6.40.14= 45.71∴ Valency of Metal = Approximate atomic weight  Equivalent weight =45.7115.18=3.01≃3⇒ Exact atomic weight =15.18×3=45.54∴ molecular weight =45.54+3×80=285.54