Understanding Chemical Reactions and Thermodynamics

Posted on Feb 15, 2025 in Chemistry

Test Results

  1. When two or more pure substances mix to form a gas or solution, absorption or release of heat occurs; this is called a reaction.
  2. Calor (This seems to be an error, likely intended to be ‘Specific Heat’). Specific Heat is the ratio of the specific heat capacity of a substance to the heat capacity of water, the latter measured at a temperature close to 17°C. Correct
  3. The energy balance is: energy that accumulates within the system, less energy consumed within the system. Correct
  4. The energy balance is: energy that accumulates within the system equals the energy that enters the system, plus the energy generated within the system, less the energy that leaves the system, less the energy consumed within the system. Correct
  5. The heat of reaction for incomplete reactions can be calculated from the reactants. Incorrect
  6. The set of independent intensive properties needed to define the system’s state can be determined by the phase rule. Correct
  7. The simplest and most accurate method is to calculate enthalpy changes using average heat capacities, rather than using tabular data. (This statement is generally **incorrect**. Using tabular data, especially if it’s temperature-dependent, is usually more accurate.)
  8. The non-steady state energy balance consists of kinetic energy, potential energy, work, the volume integral against the pressure differential, and a term due to the loss of mechanical energy by irreversible conversion. Correct
  9. In flow conversion, 1 L/h is equal to 2.8 x 10-7 m3/s. Correct
  10. In the Othmer plot, the vapor pressure of a substance and a reference substance are related and compared to the heats of vaporization.
  11. Converting the density of water, 1 g/cm3, to the International System of Units is equal to 1 kg/m3. Incorrect (It should be 1000 kg/m3)
  12. In calculating the standard heats of formation, the reaction must necessarily correspond to what really takes place at constant temperature. It must represent a fictitious process for the formation of a compound from its elements. Incorrect
  13. Internal energy is a microscopic measure of molecular, atomic, or subatomic energies, all of which follow the rules of conservation of microscopic dynamical systems. Correct
  14. The heat capacity of water does not vary with temperature. Incorrect
  15. Enthalpy and internal energy are state functions because they depend only on the initial and final states, not on the path taken. Correct
  16. The definition of a mole is the amount of a substance that contains as many elementary entities as the number of atoms in 0.012 kg of carbon-12. Correct
  17. The relationship between Celsius and Fahrenheit scales is 1.8°C = 1°F. Incorrect (It should be Δ1.8°C = Δ1°F, or more precisely, °F = 1.8°C + 32)
  18. The internal energy of a system is the amount of heat supplied to the system minus the work done by the system. Correct
  19. A reversible process is the best that can ideally be achieved and is a measure of the maximum efficiency that can be achieved in processes, since all real processes are irreversible. Correct
  20. The enthalpy change of phase transition equals the definite integral between two temperatures of the heat capacity at constant pressure resulting from the temperature. Incorrect
  21. The absolute temperature scales are Celsius and Fahrenheit. Incorrect (Kelvin and Rankine are absolute scales)
  22. Under standard conditions for heats of reaction, the enthalpy change and all constituents must be expressed with respect to the reference state of 25°C and 1 atm. Correct
  23. Dimensions are the basic concepts of measurement, such as length, time, mass, temperature, and so on. Correct
  24. The rules for handling units are to treat them as algebraic symbols that can be added, subtracted, multiplied, or divided. Different units should not be directly added or subtracted, but can be multiplied or divided, and units can be canceled in this way. Incorrect
  25. If the material balance equation is non-linear, graphs can be made by hand or by using a computer program for solving roots. Correct
  26. If there is no accumulation of energy, but there is mass flow, heat minus work is related to enthalpy, kinetic energy, and potential energy. Correct
  27. Only relative enthalpies can be determined. Correct
  28. An isometric or isochoric process is a process that occurs at constant volume. (The original statement incorrectly said “constant temperature”). Corrected
  29. Volume is related to the mass per unit volume (density). Correct