Question

If you look at the table of specific heat values for different metals, they are all so different from one another. The difference is mainly because specific heat is expressed as energy per unit mass. If specific heat were given as energy per mole, the values would be very similar. It is, in fact, this similarity of the molar specific heats of metals, which is the basis for the Law of Dulong and Petit. The law of Dulong and Petit states that the heat capacity of a metal in J/g⋅ ^oC multiplied by the molar mass of the metal in grams/mole is a constant:

Cp x Molar Mass = 25 J/mol⋅^oC

Using the heat capacity value of 0.3852J/mol⋅^oC , solve for the molar mass of the metal. (Put your answer in 4 significant figures)

Based on your calculations from above, which metal is this?

Answer 1

From given formula,

C_p * molar mass = 25 J / mol ^oC.

Now put the value of heat capacity in given formula

Since the value of heat capacity will contain unit g in it instead of mol because as per the definition heat capacity is the amount of heat required to raise the temperature of 1g substance by 1^oC. Therefore unit is J / g ^oC.

0.3850 J/ g ^oC * Molar mass = 25 J/ mol ^oC

Molar mass =

25J/molo 0.3852J/gºC

Molar mass = 64.9013 g/ mol

If we look at the periodic table the atomic mass of zinc is 65.39 g/mol and the value 64.9013 will be closer to this. Therefore the metal present in reaction is zinc and its calculated molar mass is 64.90 g/mol.

If you find any mistake please mention in the comment box.

Thanks.