How do I calculate vapor pressure of water?

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How do I calculate vapor pressure of water?

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Answer 1 · 2014-12-20T10:12:32

You could use Antoine's equation to calculate the vapor pressure of water. Antoine's equation is a vapor pressure equation that describes the relationship between vapor pressure and temperature for pure components. So,

${log}_{10} p = A - \frac{B}{C + T}$ $log_10p = A - B/(C + T)$ , where

$p$ $p$ - the vapor pressure;
$T$ $T$ - temperature;
$A$ $A$ , $B$ $B$ , $C$ $C$ - constants specific to each substance.

You'd get $p = 10^{A - \frac{B}{C + T}}$ $p = 10^(A-B/(C + T))$ .

This equation is usually used with two sets of paramaters, a low-pressure paramater that describes the vapor pressure curve up to the normal boiling point, and a second paramater that covers the range from boiling point to critical point.

So, for water, the two sets of paramaters are

SET 1. $A$ $A$ = 8.07131, $B$ $B$ = 1730.63, $C$ $C$ = 233.426 for temeperatures between $1$ $1$ and $100^{\circ} C$ $100^@C$ ;
SET 2. $A$ $A$ = 8.14019, $B$ $B$ = 1810.94, $C$ $C$ = 244.485 for temperatures betwen $99$ $99$ and $374^{\circ} C$ $374^@C$ .

Notice that you can use both sets of paramaters for temeperatures between $99$ $99$ and $100^{\circ} C$ $100^@C$ .

Here's a diagram of what an Antoine curve would look like

![http://en.wikipedia.org/wiki/Vapor_pressure]( useruploads.socratic.org )

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How do I calculate vapor pressure of water?

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