Which of the following units is commonly used to express heat capacity?

• A. J K^{-1}
• B. J g^{-1} K^{-1}
• C. J s^{-1}
• D. J mol^{-1} K^{-1}

Answer: (A)

Verified step by step guidance

1. Understand that heat capacity is a measure of the amount of heat required to raise the temperature of a substance by one degree Kelvin (or Celsius).
2. Recall that the unit of heat capacity must include energy (Joules, J) and temperature change (Kelvin, K) in the denominator to represent heat per degree change.
3. Analyze each option: J K^{-1} means Joules per Kelvin, which matches the definition of heat capacity (energy per temperature change).
4. J g^{-1} K^{-1} represents specific heat capacity (energy per gram per degree), which is related but not the same as heat capacity itself.
5. J mol^{-1} K^{-1} represents molar heat capacity (energy per mole per degree), also related but more specific; J s^{-1} is a unit of power (Watts), not heat capacity.