# Suggested Homework Set 1

## BCH 341 – ASU ONLINE – iCourse – Spring 2018

J.P. Allen, BioPhysical Chemistry, Wiley-Blackwell, 2008. (free PDF version for ASU students)

Chapter 1: problems 1, 2, 6 & 10

Chapter 2: problems 5, 9, 14 & 16.

1-1A: Air can often be modeled thermodynamically as an ideal gas mixture of 80% nitrogen and 20% oxygen gas.  Using these assumptions, predict the mean atmospheric pressure in Flagstaff, AZ on a summer day when the temperature is 77°F.  To make this prediction more mathematically tractable it is reasonable to assume an isothermal atmosphere.

1-2A: Derive an analytical expression for the thermal expansion coefficient (α) and the isothermal compressibility (κT) for gases which obey the ‘hard sphere’ equation of state (EoS):

Where P is the pressure, n is the number of moles, R is the gas constant, T is the temperature, V is the volume and b is the volume per mole that is occupied by the molecules.

1-2B – As an extension to this problem, derive the same analytical expressions as discussed above for the Van der Waals equation of state.

1-3A: As discussed in the ‘Enthalpy Changes of Biochemical Reactions’ section of J. Allen’s book ‘BioPhysical Chemistry’,  the thermodynamic properties of foods can be discussed in terms of the enthalpy of combustion per gram of food.  Do you get more energy from the metabolism of one gram of sugar or one gram of fat?  (answer this question quantitatively and with as much thermodynamic detail as possible)

This question can be addressed by calculating the energy of one gram of sugar and fat.  The most common and/or simplest methods for addressing the problem above is to first assume something about ‘metabolism’.  Typically, the it’s the assumption of full combustion of all compounds. The second step (assumption) would be to pick a common sugar and a common fat to represent these two biochemical compound groups.  The final step would then be to use standard heat of formation tables to calculate the standard state heat of combustion and compare.

1-3B: Use an arithmetic method (e.g., Kharash equation and/or method) to estimate the energy content based on structure or empirical formula.  Please see the following reference to help provide background and a procedure for this method of estimating the energy content of metabolites: G. Banfalvi, Biochemical Education 27 (1999) 79-82.

1-3C: This question can also be addressed experimentally through a technique like bomb calorimetry, which directly measures the heat of combustion.  Since, we do not have access to an actual calorimeter in this class, please use a bomb calorimetry simulator (Prof. Bertrand’s ‘simulation experiments’: http://web.mst.edu/~gbert/cal/cal.html) and address the question using experimental or simulated bomb calorimetry data.

1-3D: This question can also be addressed computationally through thermochemistry electronic structure methods.   There are a lot of computational programs available that can be used to perform thermochemistry computations.  For simplicity, it is recommended that you start with a simple online molecular calculator, molCalc (http://molcalc.org/).

Strategies for working problems – FIND AS MANY GOOD RESOURCES AS POSSIBLE.  I think we all start with google.  However, besides the primary online resources like google search, wikipedia and web of science (or related) search, I also list a few textbooks on this subject matter:

• Kuriyan, Konforti & Wemmer, The Molecules of Life: Physical and Chemical Principles. Chapters 3 & 6.
• Phillips, Kondev, Theriot & Garcia, Physical Biology of the Cell., 2nd Ed., Chapter 5.
• Callen, Thermodynamics & an Introduction to Thermostatistics., 2nd Ed., Chapters 1 & 2.