Gas constant-volume thermometry — hydrogen range: What is the typical operating temperature range (°C) for a hydrogen gas constant-volume thermometer?

Introduction / Context:
Gas thermometers form the basis of thermodynamic temperature scales because gas properties can be related accurately to temperature. In constant-volume gas thermometry, pressure changes with temperature are measured. Different gases are chosen for different ranges to maintain sensitivity and avoid condensation or chemical reactivity issues. This item asks for the typical range for a hydrogen constant-volume thermometer (CVGT).

Given Data / Assumptions:

• Hydrogen is used as the working gas at suitable pressures.
• We refer to practical ranges commonly cited in instrumentation texts.
• Temperature is expressed in degrees Celsius.

Concept / Approach:
Hydrogen remains stable and gives good sensitivity at elevated temperatures and is often assigned to the higher portion of gas-thermometer service, whereas helium/nitrogen are used differently depending on the low-temperature needs. A commonly taught practical range for a hydrogen CVGT is about 100 to 500°C, covering the mid-to-high span where hydrogen behaves reliably and the apparatus materials can be managed safely.

Step-by-Step Solution:

Verification / Alternative check:
Tabulated instrument ranges in classic metrology sources indicate hydrogen’s use in higher-temperature gas thermometry, roughly spanning hundreds of degrees Celsius.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing constant-volume gas thermometers with resistance/thermocouple ranges; gas thermometers are reference-grade but not universally used due to practical constraints.

Final Answer:
100 to 500