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what is the vapor pressure of water at 25oc? at 30oc? where would you look to find these values?

Written By Saturday, April 9, 2022 Add Comment Edit
Vapour pressure of water (0–100 °C)[ane]
T, °C T, °F P, kPa P, torr P, atm
0 32 0.6113 4.5851 0.0060
5 41 0.8726 6.5450 0.0086
10 50 ane.2281 9.2115 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 iv.2455 31.8439 0.0419
35 95 five.6267 42.2037 0.0555
40 104 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
threescore 140 19.9320 149.5023 0.1967
65 149 25.0220 187.6804 0.2469
lxx 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 seventy.1170 525.9208 0.6920
95 203 84.5290 634.0196 0.8342
100 212 101.3200 759.9625 1.0000

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

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

Approximation formulas [edit]

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

Name Formula Description
"Eq. 1" (August equation) P = exp ⁡ ( 20.386 − 5132 T ) {\displaystyle P=\exp \left(twenty.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 − B C + T {\displaystyle \log _{10}P=A-{\frac {B}{C+T}}} , where the temperatureT is in degrees Celsius (°C) and the vapour force per unit areaP is in mmHg. The (unattributed) constants are given equally
A B C T min , °C T max , °C
8.07131 1730.63 233.426 1 99
eight.14019 1810.94 244.485 100 374
August-Roche-Magnus (or Magnus-Tetens or Magnus) equation P = 0.61094 exp ⁡ ( 17.625 T T + 243.04 ) {\displaystyle P=0.61094\exp \left({\frac {17.625T}{T+243.04}}\right)} , where temperatureT is in °C and vapour pressureP is in kilopascals (kPa)

Equally described in Alduchov and Eskridge (1996).[ii] Equation 21 in [two] provides the coefficients used here. Run across also give-and-take of Clausius-Clapeyron approximations used in meteorology and climatology.

Tetens equation P = 0.61078 exp ⁡ ( 17.27 T T + 237.3 ) {\displaystyle P=0.61078\exp \left({\frac {17.27T}{T+237.3}}\right)} , where temperatureT is in °C andP is in kPa
The Buck equation. P = 0.61121 exp ⁡ ( ( 18.678 − T 234.5 ) ( T 257.xiv + T ) ) {\displaystyle P=0.61121\exp \left(\left(18.678-{\frac {T}{234.5}}\correct)\left({\frac {T}{257.14+T}}\correct)\right)} , where T is in °C and P is in kPa.
The Goff-Gratch (1946) equation.[3] (See article; besides long)

Accuracy of different formulations [edit]

Hither is a comparison of the accuracies of these different explicit formulations, showing saturation vapour pressures for liquid water in kPa, calculated at half dozen temperatures with their percentage fault 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 (+seven.85%) 0.6056 (-0.93%) 0.6109 (-0.06%) 0.6108 (-0.09%) 0.6112 (-0.01%) 0.6089 (-0.forty%)
twenty two.3388 ii.3755 (+ane.57%) 2.3296 (-0.39%) 2.3334 (-0.23%) 2.3382 (+0.05%) ii.3383 (-0.02%) 2.3355 (-0.14%)
35 5.6267 5.5696 (-1.01%) 5.6090 (-0.31%) 5.6176 (-0.16%) 5.6225 (+0.04%) v.6268 (+0.00%) 5.6221 (-0.08%)
50 12.344 12.065 (-2.26%) 12.306 (-0.31%) 12.361 (+0.13%) 12.336 (+0.08%) 12.349 (+0.04%) 12.338 (-0.05%)
75 38.563 37.738 (-ii.14%) 38.463 (-0.26%) 39.000 (+1.13%) 38.646 (+0.40%) 38.595 (+0.08%) 38.555 (-0.02%)
100 101.32 101.31 (-0.01%) 101.34 (+0.02%) 104.077 (+2.72%) 102.21 (+one.10%) 101.31 (-0.01%) 101.32 (0.00%)

A more detailed word of accurateness and considerations of the inaccuracy in temperature measurements is presented in Alduchov and Eskridge (1996). The analysis here shows the uncomplicated unattributed formula and the Antoine equation are reasonably accurate at 100 °C, just quite poor for lower temperatures above freezing. Tetens is much more accurate over the range from 0 to fifty °C and very competitive at 75 °C, but Antoine's is superior at 75 °C and above. The unattributed formula must have zero error at effectually 26 °C, only is of very poor accuracy outside a very narrow range. Tetens' equations are generally much more accurate and arguably simpler for employ at everyday temperatures (due east.g., in meteorology). As expected, Cadet's equation for T > 0 °C is significantly more accurate than Tetens, and its superiority increases markedly higher up 50 °C, though it is more complicated to employ. The Cadet equation is even superior to the more complex Goff-Gratch equation over the range needed for applied meteorology.

Numerical approximations [edit]

For serious computation, Lowe (1977)[4] adult 2 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 utilize nested polynomials for very efficient ciphering. However, at that place are more contempo reviews of possibly superior formulations, notably Wexler (1976, 1977),[5] [vi] reported past Flatau et al. (1992).[7]

Examples of mod use of these formulae can additionally be institute in NASA's GISS Model-Due east and Seinfeld and Pandis (2006). The quondam is an extremely simple Antoine equation, while the latter is a polynomial.[viii]

Graphical pressure dependency on temperature [edit]

Encounter also [edit]

  • Dew point
  • Gas laws
  • Tooth mass
  • Clausius–Clapeyron relation
  • Goff-Gratch equation
  • Antoine equation
  • Tetens equation
  • Arden Buck equation
  • Lee–Kesler method

References [edit]

  1. ^ Lide, David R., ed. (2004). CRC Handbook of Chemistry and Physics, (85th ed.). CRC Press. pp. 6–8. ISBN978-0-8493-0485-9.
  2. ^ a b Alduchov, O.A.; Eskridge, R.E. (1996). "Improved Magnus grade approximation of saturation vapor pressure". Journal of Applied Meteorology. 35 (4): 601–9. Bibcode:1996JApMe..35..601A. doi:x.1175/1520-0450(1996)035<0601:IMFAOS>two.0.CO;2.
  3. ^ Goff, J.A., and Gratch, S. 1946. Low-pressure level properties of h2o from −160 to 212 °F. In Transactions of the American Order of Heating and Ventilating Engineers, pp 95–122, presented at the 52nd annual meeting of the American Order of Heating and Ventilating Engineers, New York, 1946.
  4. ^ Lowe, P.R. (1977). "An approximating polynomial for the computation of saturation vapor pressure". Journal of Practical Meteorology. 16 (1): 100–4. Bibcode:1977JApMe..sixteen..100L. doi:10.1175/1520-0450(1977)016<0100:AAPFTC>2.0.CO;2.
  5. ^ Wexler, A. (1976). "Vapor pressure formulation for water in range 0 to 100°C. A revision". Periodical of Research of the National Agency of Standards Department A. 80A (5–6): 775–785. doi:x.6028/jres.080a.071. PMC5312760. PMID 32196299.
  6. ^ Wexler, A. (1977). "Vapor pressure formulation for ice". Periodical of Enquiry of the National Bureau of Standards Section A. 81A (1): five–20. doi:10.6028/jres.081a.003.
  7. ^ Flatau, P.J.; Walko, R.L.; Cotton, W.R. (1992). "Polynomial fits to saturation vapor pressure". Journal of Applied Meteorology. 31 (12): 1507–13. Bibcode:1992JApMe..31.1507F. doi:ten.1175/1520-0450(1992)031<1507:PFTSVP>2.0.CO;2.
  8. ^ Clemenzi, Robert. "Water Vapor - Formulas". mc-calculating.com.

Further reading [edit]

  • "Thermophysical properties of seawater". Matlab, EES and Excel VBA library routines. MIT. 20 Feb 2017.
  • Garnett, Pat; Anderton, John D; Garnett, Pamela J (1997). Chemistry Laboratory Manual For Senior Secondary School. Longman. ISBN978-0-582-86764-2.
  • Spud, D.1000.; Koop, T. (2005). "Review of the vapour pressures of ice and supercooled water for atmospheric applications". Quarterly Journal of the Royal Meteorological Society. 131 (608): 1539–65. Bibcode:2005QJRMS.131.1539M. doi:10.1256/qj.04.94.
  • Speight, James G. (2004). Lange'due south Handbook of Chemistry (16th ed.). McGraw-Hil. ISBN978-0071432207.

External links [edit]

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

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Source: https://en.wikipedia.org/wiki/Vapour_pressure_of_water

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