I know how to calculate the specific heat, but not molar specific heat. What is molar specific heat and how do you calculate it?
1 Answer
Specific heat has the units of $\mathrm{J/(K\cdot kg)}$.
Molar specific heat is in units of $\mathrm{J/(K\cdot mol)}$, and is the amount of heat needed (in joules) to raise the temperature of $1$ mole of something, by $1$ kelvin (assuming no phase changes).
So, the conversion factor you need, from dimension analysis, will have unit $\pu{kg/mol}$.
$\pu{kg/mol}$ is the SI unit for molar mass.
Multiply the specific heat by the molar mass to get the molar specific heat.
For example, the molar mass of water is $\approx \pu{0.018 kg/mol}$.
The specific heat of water is $\approx 4186\ \mathrm{J/(K\cdot kg)}$.
So the molar specific heat of water is $4186\ \mathrm{J/(K\cdot kg)} \times \pu{0.018 kg/mol} \approx 75\ \mathrm{J/(K\cdot mol)}$
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$\begingroup$ In this case, exactly what is this "molar specific heat" that we obtain in the end? At constant volume/pressure? $\endgroup$– user33789Sep 17, 2016 at 2:24