Question

Answer the following:
(a) The triple-point of water is a standard fixed point in modern thermometry. Why? What is wrong in taking the melting point of ice and the boiling point of water as standard fixed points (as was originally done in the Celsius scale)?
(b) There were two fixed points in the original Celsius scale as mentioned above which were assigned the number 0 °C and 100 °C respectively. On the absolute scale, one of the fixed points is the triple-point of water, which on the Kelvin absolute scale is assigned the number 273.16 K. What is the other fixed point on this (Kelvin) scale?
(c) The absolute temperature (Kelvin scale) T is related to the temperature tc on the Celsius scale by
tc = T – 273.15
Why do we have 273.15 in this relation, and not 273.16?
(d) What is the temperature of the triple-point of water on an absolute scale whose unit interval size is equal to that of the Fahrenheit scale?

Answer 1

(a) The melting of ice and boiling point of water are pressure depended conditions and depends upon varies as impurities are dissolved in it .while Triple point of water is a unique condition of pressure and temperature . so, melting point of ice and boiling point of water are not taken as standard fixed point.


(b) other fixed point on the absolute scale or Kelvin scale is 0K, or absolute zero . because in this temperature molecule taken as disappear.( A/C Charles Law )

(c) ice point on Kelvin scale is 273.15K and the corresponding value in Celcius Scale is 0°C .
So, relation b/w Celcius and Kelvin
C + 273.15 = K

Triple point of water is in 273.16K .ie. In Celcius = 0.01°C .

(d) Triple point of water on Kelvin scale = 273.16 K
number of division in Kelvin scale = 100 [ boiling point = 373.15K , melting point = 273.15 K ]
Total number of divisions in Fahrenheit scale = 180 [ melting point= 32°F , boiling point = 212°F ]

A/c to question,
Triple point of water on absolute scale having 180 divisions .
Then, T = 273.16× 180/100 = 491.69