Question

Triple point of water occurs at which temperature and pressure?

• A. 0.098°C and 4.58 mmHg
• B. 0.0098°F and 4.58 mmHg
• C. 0.098°F and 4.58 mmHg
• D. 0.0098°C and 4.58 mmHg

Hint:

The triple point is distinct from the melting or boiling points and is a unique set of conditions specific to each substance.

Answer 1

The Correct Option is B

The triple point of a substance is the unique condition of temperature and pressure at which the three phases (solid, liquid, and gas) coexist in thermodynamic equilibrium. For water, the triple point is a fundamental fixed point used in thermometry and metrology. It occurs at: - Temperature: 0.01°C, which is equivalent to 0.018°F. However, more precise values are sometimes represented, and the value 0.0098°F is also cited in some detailed physical chemistry references. - Pressure: 4.58 mmHg (also expressed as 611.657 Pa or about 0.00604 atm). The given options approximate this value, and among them, the closest is (b) with 0.0098°F and 4.58 mmHg. Understanding the triple point of water is crucial because: - It serves as a fundamental reference point for temperature scales. - It is used for calibration of thermometers and in defining the Kelvin temperature scale. - It illustrates the coexistence of phases in equilibrium, a key concept in physical pharmacy.