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How is mm of Hg per degree Celsius converted to kPa per degree Celsius? I also need the equation for computing the value of A (slope) in mm of Hg per degree Celsius.

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    $\begingroup$ Is this a homework question? $\endgroup$
    – Neo
    Commented Sep 22, 2014 at 17:51
  • $\begingroup$ This is not a homework question. $\endgroup$
    – user903
    Commented Sep 23, 2014 at 5:01

2 Answers 2

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You can convert mm Hg to kPa with the conversion factor $0.133322368\ \mathrm{kPa\ mmHg^{-1}}$.

Saturation vapor pressure as a function of temperature is

$$ e_s(T) = e_{s0}\exp\left[\left(\dfrac{L_v(T)}{R_v}\right)\left(\dfrac{1}{T_0} -\dfrac{1}{T} \right)\right], $$

where $L_v(T)$ is the specific enthalpy of vaporization, $R_v$ is the specific gas constant for water vapor, $T_0$ is reference temperature (273.15 K) and $e_{s0}$ is the saturation vapor pressure at $T_0$ (611 Pa).

You can find the slope of this curve by taking the derivative $\dfrac{d e_s}{dT}$.

Note that the units of $e_s$ and $T$ are Pa and K respectively in the equation above.

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  • $\begingroup$ he could also do it through wolfram alpha if its only a few conversions =) $\endgroup$
    – Neo
    Commented Sep 22, 2014 at 20:39
  • $\begingroup$ Well, Thank you for replying. I know the relation between kPa and mmHg. But I need to express the slope in mmHg/degree celsius instead of kPa/degree celsius. I need an equation for finding that. $\endgroup$
    – user903
    Commented Sep 23, 2014 at 5:05
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finally i could find out that both units are not compatible to convert. Little bit speculated about the fact.
The equation for finding the slope in mmHg/°C = 4098*(4.584*exp(17.27*T/237.3+T))/(T+237.3)^2.

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