BackOxygen diffuses from the surface of insects to the interior through tiny tubes called tracheae. An average trachea is about 2 mm long and has cross-sectional area of 2 x 10-9 m2. Assume the concentration of oxygen inside is half what it is outside in the atmosphere. Calculate the diffusion rate J. Assume the diffusion constant is 1 x 10-5 m2/s.
The 2010 Nobel Prize in Physics was awarded for the discovery of graphene, a two-dimensional form of carbon in which the atoms form a two-dimensional crystal-lattice sheet only one atom thick. Predict the molar specific heat of graphene. Give your answer as a multiple of R.
In the van der Waals equation of state, the constant b represents the amount of “unavailable volume” (per mole) occupied by the molecules themselves. Thus V is replaced by (V-nb), where n is the number of moles. For oxygen, b is about 3.2 x 10-5 m3 /mol. Estimate the diameter of an oxygen molecule.
For oxygen gas the van der Waals constants are a = 0.14 N·m4/mol2 and b = 3.2 x 10-5 m3/mol. Using these values, graph six curves of pressure vs. volume between V = 2 x 10-5 m3 and 2.0 x 10-4 m3, for 1 mol of oxygen gas at temperatures of 80 K, 100 K, 120 K, 130 K, 150 K, and 170 K. From the graphs determine approximately the critical temperature for oxygen.
Estimate the time needed for a glycine molecule (see Table 18–3) to diffuse a distance of 25μm in water at 20°C if its concentration varies over that distance from 1.00 mol/m³ to 0.50 mol/m³. Compare this “speed” to its rms (thermal) speed. The molecular mass of glycine is about 75 u.
A scuba tank has a volume of 3100 cm³. For very deep dives, the tank is filled with 50% (by volume) pure oxygen and 50% pure helium. What is the ratio of the average kinetic energies of the two types of molecule?
A 1.0-mol sample of helium gas has a temperature of 18°C. What is the total kinetic energy of all the gas atoms in the sample?