How to Calculate Molar Heat Capacity

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The molar heat capacity of a substance is the amount of energy required to raise one mole of the substance by one degree. The standard unit is joules per mol K. A periodic table typically lists the specific heat capacity of an element. Specific heat differs from molar heat capacity in that it is measured per gram instead of per mole. Depending on the information you have and the substance in question, calculating the molar heat capacity of a substance can be a simple conversion or a more involved calculation.

  1. Determine the Specific Heat

  2. Determine the specific heat of the substance. If the substance is made of a single element, the specific heat is listed in many periodic tables. For example, the specific heat of silver is about 0.23 J/g*K. If the substance is a compound of multiple elements, you will need to verify its specific heat either experimentally, or from an already-existing document (see Resources for a table of common specific heats).

  3. Calculate Molar Mass

  4. Calculate the molar mass of the substance. The periodic table lists the molar mass of each element. If it is a compound, the molar mass must be calculated through ratios. For example, one mole of water involves 2 parts hydrogen and 1 part oxygen. The molar mass of water is obtained by multiplying each of these parts by the corresponding masses of the elements:

    2 x (1 g/mol hydrogen) + (16 g/mol oxygen) = 18 g/mol water

  5. Multiply Specific Heat by Molar Mass

  6. Multiply the specific heat of the substance by the molar mass of the substance. This results in the molar heat capacity of the substance, in joules per mol K. For water, for example, the specific heat is given as roughly 4.184 J/(g*K). Multiply this by the molar mass:

    4.184 x 18 = 75.312 J/(mol*K)

References

About the Author

Serm Murmson is a writer, thinker, musician and many other things. He has a bachelor's degree in anthropology from the University of Chicago. His concerns include such things as categories, language, descriptions, representation, criticism and labor. He has been writing professionally since 2008.

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