Question

The specific heat of a metal was found to be 0.38 J/g. Degree C. When 0.5007 g of this metal was heated in a stream of chlorine gas, it produced 1.0586 g of a metal chloride, MCl_g. Determine the formula of the metal chloride and the accurate atomic weight of the metal. What is the color of the chloride? (Consult the Handbook of Chemistry and Physics, Physical Constants of Inorganic Compounds, available in the Library reference section)

Answer 1

Let the formula of the metal chloride be MCl_x

As per Dulong's Petits law,

specific heat*atomic mass of the metal = 25

thus, atomic mass of the metal = 65.79 g/mole

Now, moles of metal in 0.5007 g of it = mass/molar mass = 0.5007/65.79 = 0.0076

mass of Cl in the metal chloride = 1.0586 - 0.5007 = 0.5579

Thus, moles of Cl in the chloride sample = 0.5579/35.5 = 0.0157

Thus, M & Cl are present in the molar ratio of 0.0076:0.0157 = 1:2

Thus, the formula of the compound is MCl₂

Now, moles of M in the compound = (1/2)*moles of Cl = (1/2)*0.0157 = 0.00785

Thus, molar mass of M = mass/moles = 0.5007/0.00785 = 63.78 g/mole