If the humidity in a room of volume 410 m3 at 25 ∘C is 70%, what mass of water can still evaporate from an open pan? Express your answer using two significant figures.

Answer :

Answer:

[tex]m=1864.68\ g[/tex]

Explanation:

Given:

volume of air in the room, [tex]V=410\ m^3[/tex]

temperature of the room, [tex]T=25+273=298\ K[/tex]

Saturation water vapor pressure at any temperature T K is given as:

[tex]p_{sw}=\frac{e^{(77.3450 + 0.0057\times T - \frac{ 7235}{T} )}}{T^{8.2}}[/tex]

putting T=298 K we have

[tex]p_{sw}=3130\ Pa[/tex]

The no. of moles of water molecules that this volume of air can hold is:

Using Ideal gas law,

[tex]P.V=n.R.T[/tex]

[tex]n=\frac{P_{sw}.V}{R.T}[/tex]

[tex]n=\frac{3130\times 410}{8.314\times 298}[/tex]

[tex]n=518\ moles[/tex] is the maximum capacity of the given volume of air to hold the moisture.

Currently we have 80% of n, so the mass of 20% of n:

[tex]m=(20\%\ of\ n)\times M}[/tex]

where;

M= molecular mass of water

[tex]m=0.2\times 518\times 18[/tex]

[tex]m=1864.68\ g[/tex] is the mass of water that can vaporize further.

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