A laboratory must design an experiment to determine which of two isotopic samples—…
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A laboratory must design an experiment to determine which of two isotopic samples—20Ne(g) or 22Ne(g)—more closely follows ideal-gas behavior at cryogenic temperatures. The apparatus can measure pressure to within ±0.02 atm and volume to within ±0.05 mL for a fixed amount of gas.
Both samples can be cooled to 80 K and compressed up to 350 atm in the same 250.0 mL stainless-steel cell.
(a) Propose a detailed experimental procedure (including the variables to be measured, the range of conditions, and the calculations to be performed) that would allow the lab to compare the non-ideal behavior of the two isotopes quantitatively.
(b) Using kinetic-molecular reasoning, predict which isotope will display the larger deviation from the ideal-gas law at 80 K and 350 atm. Address both attractive interactions and molecular (atomic) size in your explanation.
(c) Discuss two potential sources of systematic error in your proposed experiment and explain how each would affect the calculated compressibility factors for the gases.
(d) Suggest a modification to the procedure that would improve the precision of distinguishing between the isotopes’ deviations without changing the available instrumentation. Justify how your modification addresses one of the errors identified in part (c).