Gas constant-volume thermometry with nitrogen: a nitrogen gas constant-volume thermometer is particularly suitable for measuring temperatures in which range relative to 100 °C?

Introduction / Context:
Gas thermometers are primary thermometric standards because gas properties are well described by equations of state. In practice, specific gases are chosen for different temperature regimes. Hydrogen is favored for very low temperatures due to minimal condensation issues, whereas nitrogen is commonly used for higher ranges in constant-volume thermometry.

Given Data / Assumptions:

• Thermometer type: constant-volume gas thermometer.
• Working gas: nitrogen (chemically inert and readily available).
• We compare its suitability with respect to 100 °C.

Concept / Approach:
In a constant-volume gas thermometer, pressure variation tracks temperature at fixed volume (P proportional to T in Kelvin for ideal behavior). Nitrogen is stable and convenient well above ambient and is a traditional choice for temperatures exceeding the boiling point of water. Below 0 °C and at cryogenic temperatures, hydrogen or helium are preferred to avoid liquefaction and to maintain near-ideal behavior.

Step-by-Step Solution:
Recognize nitrogen’s operating envelope: robust at moderate to high temperatures.Contrast with hydrogen/helium for sub-zero or cryogenic ranges.Conclude that nitrogen constant-volume thermometers are best suited for temperatures greater than 100 °C among the given choices.

Verification / Alternative check:
Calibration tables and metrological references group nitrogen with mid-to-high temperature service for gas thermometry, while special gases handle extremes.

Why Other Options Are Wrong:
0–100 °C: Usable, but nitrogen’s canonical niche in textbooks is above 100 °C.< 0 °C: Risk of non-idealities and condensation; other gases are favored.> 50 °C: Too broad; standard pedagogy specifies above 100 °C.Exactly 100 °C only: Incorrect; a thermometer covers ranges, not single points.

Common Pitfalls:
Confusing constant-volume with constant-pressure gas thermometers, or assuming all gases are equally suitable across all temperatures. Gas selection impacts measurement uncertainty and practical construction.

Final Answer:
> 100 °C