Two ideal gas thermometers A and B use oxygen and hydrogen respectively. The following observations are made:
`{:("Temperature","Pressure","Pressure"),(,"thermometer A","thermometer B"),("Triple - point water",1.250 xx10^(5) Pa,0.200 xx 10^(5) Pa),("Normal melting point of sulphur",1.797 xx10^(5)Pa,0.287 xx10^(5)Pa):}`
(a) What is the absolute temperature of normal melting point of sulphur as read by thermometers A and B ?
(b) What do you think is the reason behind the slight difference in answers of thermometers A and B ? (The thermometers are not faulty). What further procedure is needed in the experiment to reduce the discrepancy between the two readings ?

Explanation

(a) `T_(Lambda) = 392.69 K, T_(B) = 391.98 K`, (b) The discrepancy arises because the gases are not perfectly ideal To reduce the discrepancy. readings should be taken for lower and lower pressures and the plot between temperature measured versus absolute pressure of the gas at triple point should be extrapolated to obtain temperature in the limit pressure tends to zero, when the gases approach ideal gas behaviour.