PCAT Chemical Processes – Molar Heat Capacities
- Feb 19, 2018
- PCAT Question of the Day
The molar heat capacities (J/mole K) for zinc, copper, silver, and gold is 25.2, 24.5, 24.9, and 25.6, respectively. If 1 mole of each substance is heated until the temperature increases by 10K, which metal required the addition of the most heat?
Click for Explanation
This question asks you to apply information on molar heat capacities to determine the most energetically intensive material. Since the change in temperature and the quantity of each substance is constant, the difference in molar heat capacities dictates the energy requirements for each substance.
Molar heat capacity tells you how much energy (J) is necessary to increase one mole of a substance by 1 K. Therefore, the higher the molar heat capacity, the more energy required. In the question above, gold has the highest molar heat capacity and therefore requires the greatest amount of heat. The calculations are given below.
Energy = (molar heat capacity) x (# of moles) x (change in temperature)
Zinc: (25.2 J/mole K) x (1 mole) x (10 K) = 252 J
Copper: (24.5 J/mole K) x (1 mole) x (10 K) = 245 J
Silver: (24.9 J/mole K) x (1 mole) x (10 K) = 249 J
Gold: (25.6 J/mole K) x (1 mole) x (10 K) = 256 J
Multiplying the molar heat capacity by the number of moles and the change in temperature gives you energy required. Gold requires the most heat (256 J) making answer choice D correct.
Search the Blog
Free ConsultationSchedule Now
MCAT Blog How to Review MCAT Full-Lengths
Free MCAT Practice AccountNeed great MCAT practice?
Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.Learn More