A group of students sets up an experiment in which a small sample of argon gas is…
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
A group of students sets up an experiment in which a small sample of argon gas is sealed inside a rigid glass bulb that is fitted with a pressure sensor and a digital thermometer. The interior volume of the bulb is known from a prior calibration. By slowly immersing the bulb in a series of water baths at different temperatures, the students record the simultaneous values of the gas pressure, the gas temperature, and the fixed volume.
Throughout the activity, the students’ goal is to obtain a numerical value for the universal gas constant R and to evaluate the factors that limit the accuracy of their result.
Assume argon behaves as an ideal gas over the temperature range investigated.
(1) Describe qualitatively how the measurements of pressure, volume, and temperature made in this experiment can be combined with the known amount of gas to obtain a numerical value for R.
(2) Identify two distinct sources of systematic error in the experimental setup and explain, for each one, whether the error would cause the calculated value of R to be too large or too small.
(3) The thermometer used in the experiment has a calibration uncertainty of ±1K over the relevant range. Explain how this temperature uncertainty propagates into the percent uncertainty of the final value of R. No numerical calculation is required; base your reasoning on proportional relationships.
(4) The students decide to create a graph that will yield a straight-line relationship whose slope can be used to calculate R. Specify which variable should be plotted on each axis and justify how the slope of the resulting graph is related to R. State any additional information that must be known or measured for this graphical method to work.