Vapor Pressure Of Water Torr

Pressure exerted by molecules of water vapour in gaseous class

Vapour pressure of h2o (0–100 °C)^[1]
T, °C	T, °F	P, kPa	P, torr	P, atm
0	32	0.6113	iv.5851	0.0060
5	41	0.8726	six.5450	0.0086
ten	50	one.2281	ix.2115	0.0121
15	59	1.7056	12.7931	0.0168
20	68	2.3388	17.5424	0.0231
25	77	3.1690	23.7695	0.0313
30	86	4.2455	31.8439	0.0419
35	95	five.6267	42.2037	0.0555
xl	104	7.3814	55.3651	0.0728
45	113	9.5898	71.9294	0.0946
50	122	12.3440	92.5876	0.1218
55	131	15.7520	118.1497	0.1555
60	140	19.9320	149.5023	0.1967
65	149	25.0220	187.6804	0.2469
70	158	31.1760	233.8392	0.3077
75	167	38.5630	289.2463	0.3806
80	176	47.3730	355.3267	0.4675
85	185	57.8150	433.6482	0.5706
ninety	194	70.1170	525.9208	0.6920
95	203	84.5290	634.0196	0.8342
100	212	101.3200	759.9625	i.0000

The vapour pressure level of water is the pressure exerted by molecules of water vapor in gaseous grade (whether pure or in a mixture with other gases such as air). The saturation vapour pressure level is the pressure at which water vapour is in thermodynamic equilibrium with its condensed state. At pressures college than vapour force per unit area, water would condense, whilst at lower pressures it would evaporate or sublimate. The saturation vapour pressure of water increases with increasing temperature and tin exist determined with the Clausius–Clapeyron relation. The boiling point of h2o is the temperature at which the saturated vapour pressure equals the ambient pressure.

Calculations of the (saturation) vapour pressure of h2o are commonly used in meteorology. The temperature-vapour pressure relation inversely describes the relation between the boiling indicate of water and the pressure. This is relevant to both pressure cooking and cooking at high altitude. An agreement of vapour pressure is also relevant in explaining loftier altitude breathing and cavitation.

Approximation formulas [edit]

There are many published approximations for calculating saturated vapour pressure over water and over water ice. Some of these are (in approximate order of increasing accuracy):

Name

Formula

Description

"Eq. ane" (August equation)

P=\exp \left(20.386-{\frac {5132}{T}}\right)

where

P

is the vapour pressure in mmHg and

T

is the temperature in kelvins. Constants are unattributed.

The Antoine equation

\log _{x}P=A-{\frac {B}{C+T}}

where the temperature

T

is in degrees Celsius (°C) and the vapour pressure

P

is in mmHg. The (unattributed) constants are given as

$A$	$B$	$C$	$T min$ , °C	$T max$ , °C
viii.07131	1730.63	233.426	one	99
8.14019	1810.94	244.485	100	374

August-Roche-Magnus (or Magnus-Tetens or Magnus) equation

P=0.61094\exp \left({\frac {17.625T}{T+243.04}}\right)

where temperature

T

is in °C and vapour pressure

P

is in kilopascals (kPa)

As described in Alduchov and Eskridge (1996).^[two] Equation 21 in ^[2] provides the coefficients used hither. See as well discussion of Clausius-Clapeyron approximations used in meteorology and climatology.

Tetens equation

P=0.61078\exp \left({\frac {17.27T}{T+237.iii}}\right)

where temperature

T

is in °C and

P

is in kPa

The Buck equation.

P=0.61121\exp \left(\left(18.678-{\frac {T}{234.5}}\right)\left({\frac {T}{257.fourteen+T}}\correct)\right)

where

T

is in °C and

P

is in kPa.

The Goff-Gratch (1946) equation.^[three]

(See article; too long)

Accuracy of different formulations [edit]

Hither is a comparison of the accuracies of these unlike explicit formulations, showing saturation vapour pressures for liquid water in kPa, calculated at six temperatures with their percentage error from the table values of Lide (2005):

$T$ (°C)	$P$ (Lide Table)	$P$ (Eq 1)	$P$ (Antoine)	$P$ (Magnus)	$P$ (Tetens)	$P$ (Buck)	$P$ (Goff-Gratch)
0	0.6113	0.6593 (+7.85%)	0.6056 (-0.93%)	0.6109 (-0.06%)	0.6108 (-0.09%)	0.6112 (-0.01%)	0.6089 (-0.40%)
twenty	2.3388	2.3755 (+ane.57%)	ii.3296 (-0.39%)	2.3334 (-0.23%)	2.3382 (+0.05%)	2.3383 (-0.02%)	2.3355 (-0.14%)
35	5.6267	5.5696 (-1.01%)	five.6090 (-0.31%)	5.6176 (-0.16%)	five.6225 (+0.04%)	five.6268 (+0.00%)	five.6221 (-0.08%)
fifty	12.344	12.065 (-two.26%)	12.306 (-0.31%)	12.361 (+0.thirteen%)	12.336 (+0.08%)	12.349 (+0.04%)	12.338 (-0.05%)
75	38.563	37.738 (-two.14%)	38.463 (-0.26%)	39.000 (+one.thirteen%)	38.646 (+0.twoscore%)	38.595 (+0.08%)	38.555 (-0.02%)
100	101.32	101.31 (-0.01%)	101.34 (+0.02%)	104.077 (+ii.72%)	102.21 (+1.10%)	101.31 (-0.01%)	101.32 (0.00%)

A more detailed give-and-take of accuracy and considerations of the inaccuracy in temperature measurements is presented in Alduchov and Eskridge (1996). The analysis here shows the simple unattributed formula and the Antoine equation are reasonably authentic at 100 °C, merely quite poor for lower temperatures above freezing. Tetens is much more authentic over the range from 0 to 50 °C and very competitive at 75 °C, but Antoine's is superior at 75 °C and above. The unattributed formula must accept nothing error at effectually 26 °C, but is of very poor accuracy exterior a very narrow range. Tetens' equations are generally much more than accurate and arguably simpler for apply at everyday temperatures (eastward.g., in meteorology). As expected, Buck's equation for $T$ > 0 °C is significantly more than accurate than Tetens, and its superiority increases markedly above 50 °C, though information technology is more complicated to use. The Cadet equation is even superior to the more complex Goff-Gratch equation over the range needed for practical meteorology.

Numerical approximations [edit]

For serious computation, Lowe (1977)^[4] developed two pairs of equations for temperatures above and below freezing, with different levels of accuracy. They are all very accurate (compared to Clausius-Clapeyron and the Goff-Gratch) but utilise nested polynomials for very efficient ciphering. However, in that location are more contempo reviews of possibly superior formulations, notably Wexler (1976, 1977),^[5] ^[6] reported past Flatau et al. (1992).^[7]

Examples of modern utilize of these formulae can additionally be constitute in NASA's GISS Model-E and Seinfeld and Pandis (2006). The former is an extremely simple Antoine equation, while the latter is a polynomial.^[8]

Graphical force per unit area dependency on temperature [edit]

See as well [edit]

Dew point
Gas laws
Lee–Kesler method
Tooth mass

References [edit]

^ Lide, David R., ed. (2004). CRC Handbook of Chemistry and Physics, (85th ed.). CRC Press. pp. 6–8. ISBN978-0-8493-0485-9.
^ ^a ^b Alduchov, O.A.; Eskridge, R.E. (1996). "Improved Magnus form approximation of saturation vapor pressure level". Periodical of Applied Meteorology. 35 (iv): 601–9. Bibcode:1996JApMe..35..601A. doi:ten.1175/1520-0450(1996)035<0601:IMFAOS>2.0.CO;2.
^ Goff, J.A., and Gratch, South. 1946. Low-pressure backdrop of water from −160 to 212 °F. In Transactions of the American Social club of Heating and Ventilating Engineers, pp 95–122, presented at the 52nd almanac meeting of the American Lodge of Heating and Ventilating Engineers, New York, 1946.
^ Lowe, P.R. (1977). "An approximating polynomial for the computation of saturation vapor pressure". Journal of Applied Meteorology. xvi (1): 100–four. Bibcode:1977JApMe..16..100L. doi:10.1175/1520-0450(1977)016<0100:AAPFTC>two.0.CO;2.
^ Wexler, A. (1976). "Vapor pressure formulation for water in range 0 to 100°C. A revision". Journal of Research of the National Bureau of Standards Section A. 80A (5–half-dozen): 775–785. doi:x.6028/jres.080a.071. PMC5312760. PMID 32196299.
^ Wexler, A. (1977). "Vapor force per unit area formulation for ice". Journal of Research of the National Bureau of Standards Department A. 81A (ane): v–20. doi:10.6028/jres.081a.003.
^ Flatau, P.J.; Walko, R.Fifty.; Cotton wool, Westward.R. (1992). "Polynomial fits to saturation vapor pressure". Journal of Applied Meteorology. 31 (12): 1507–13. Bibcode:1992JApMe..31.1507F. doi:10.1175/1520-0450(1992)031<1507:PFTSVP>2.0.CO;ii.
^ Clemenzi, Robert. "H2o Vapor - Formulas". mc-computing.com.

External links [edit]

Vömel, Holger (2016). "Saturation vapor force per unit area formulations". Boulder CO: Earth Observing Laboratory, National Middle for Atmospheric Research. Archived from the original on June 23, 2017.
"Vapor Pressure Figurer". National Weather condition Service, National Oceanic and Atmospheric Assistants.