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If we heat a partially filled closed container with liquid in it, will the relative humidity ever reach 100% (assuming that the vessel is strong enough to hold infinite amount of pressure). I have read that as temperature increases the moisture carrying capacity of the air will increase hence as long as we don't add vapor to air the relative humidity will increase. But since in a closed container the temperature of the liquid also keeps on increasing, more amount of molecules are turning from liquid state to the gaseous state as well.

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  • $\begingroup$ In the enclosed container the vapor pressure for the liquid will also rise causing the boiling point of the liquid to increase, don't forget about that effect. $\endgroup$
    – Triatticus
    Commented Aug 20, 2022 at 10:15
  • $\begingroup$ Yes Indeed that is the main reason why I asked the question. As boiling point increases the temperature of the vapor above it will also increase. Which in turn brings me to the question of Relative Humidity. $\endgroup$ Commented Aug 20, 2022 at 10:25
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    $\begingroup$ In closed container at equilibrium the relative humidity is always 100%. The liquid evaporates until the partial pressure of the vapor reaches the maximum value. $\endgroup$
    – nasu
    Commented Aug 20, 2022 at 11:07
  • $\begingroup$ @nasu Please consider converting your comment to an answer (with the condition that equilibrium is assumed). $\endgroup$ Commented Aug 20, 2022 at 18:07

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In a closed container at equilibrium the relative humidity is always 100%. The liquid evaporates until the partial pressure of the vapor reaches the maximum value. If the temperature is increased the (maximum) vapour pressure increases and more liquid evaporates until the partial pressure of the vapors reaches the new vapor pressure. And is again 100% relative humidity at the new equilibrium state. If course, if there is enough liquid in the container to have both phases at equilibrium.

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  • $\begingroup$ So as long as the Temperature of the gases keeps increasing we won't have a 100% Relative Humidity. Ideally we won't attain 100% R.H. $\endgroup$ Commented Aug 21, 2022 at 15:29
  • $\begingroup$ It depends on what you mean by "ideally". You cannot increase the temperature forever. But during the non-equilibrium stages the humidity may be less than 100%. It will help if you disclose the actual purpose of your question. $\endgroup$
    – nasu
    Commented Aug 21, 2022 at 16:06
  • $\begingroup$ By ideal scenario I meant that the temperature of the air above the liquid keeps on changing at every instant of time, such that the vapour pressure never becomes equal to saturation vapour pressure. $\endgroup$ Commented Aug 22, 2022 at 4:01
  • $\begingroup$ Also a quick clarification, will the RH reach 100% without supplying heat, say after a certain duration of time? Evaporation does happen always till RH becomes 100% right? $\endgroup$ Commented Aug 22, 2022 at 6:19

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