Temperatur dan tekanan standar

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Dalam kimia dan sains lainnya, istilah temperatur dan tekanan standar (Inggris: standard temperature and pressure, disingkat STP) adalah sebuah keadaan standar yang digunakan dalam pengukuran eksperimen. Standar ini digunakan agar setiap data dalam percobaan yang berbeda-beda dapat dibandingkan. Standar yang paling umum digunakan adalah standar IUPAC dan NIST. Terdapat juga variasi standar lainnya yang ditetapkan oleh organisasi-organisasi lainnya. Standar IUPAC sekarang ini adalah temperatur 0 °C (273,15 K, 32 °F) dan tekanan absolut 100 kPa (14,504 psi)[1], sedangkan standar NIST adalah 20 °C (293,15 K, 68 °F) dan tekanan absolut 101,325 kPa (14,696 psi).

Dalam bidang industri dan komersial, kondisi standar temperatur dan tekanan bisanya perlu disebutkan untuk merujuk pada kondisi referensi standar untuk mengekspresikan volume gas dan cairan dan kuantitas lainnya. Walapun begitu, kebanyakan publikasi teknis hanya menyatakan "kondisi standar" tanpa penjelasan lebih lanjut, sehingga menimbulkan kerancuan dan kesalahan.

Definisi[sunting | sunting sumber]

Definisi lama[sunting | sunting sumber]

Dalam lima sampai enam dasarwasa terakhir, para profesional dan ilmuwan yang menggunakan sistem satuan metrik mendefinisikan kondisi referensi standar temperatur dan tekanan untuk mengekspresikan volume gas sebagai 0 °C (273,15 K) dan 101,325 kPa (1 atm). Sedangkan untuk yang menggunakan saturan Imperial adalah 60 °F (520 °R) dan 14,696 psi (1 atm). Namun kedua definisi di atas tidak lagi digunakan.

Definisi baru[sunting | sunting sumber]

Terdapat beberapa definisi kondisi referensi standar yang sekarang digunakan oleh berbagai organisasi-organisasi di dunia. Beberapa organisasi mempunyai standar yang berbeda pada masa lalu, seperti IUPAC yang mempunyai standar 0 °C dan 100 kPa (1 bar) sejak 1982 dan berbeda dengan standar lama 0 °C dan 101,325 kPa (1 atm).[2] Contoh lainnya pada industri perminyakan, dengan standar lama 60 °F dan 14.696 psi, dan standar baru (terutama di Amerika Utara) 60 °F dan 14,73 psi.

Kondisi referensi standar
Temperatur Tekanan mutlak Kelembapan relatif Organisasi
°C kPa % RH
0 100,000   IUPAC (definisi baru)[1]
0 101,325   IUPAC (definisi lama)[1], NIST[3], ISO 10780[4]
15 101,325 0[5][6] ICAO's ISA,[5] ISO 13443,[6] EEA,[7] EGIA[8]
20 101,325   EPA,[9] NIST[10]
25 101,325   EPA[11]
25 100,000   SATP[12]
20 100,000 0 CAGI[13]
15 100,000   SPE[14]
°F psi  % RH
60 14,696   SPE,[14] U.S. OSHA,[15] SCAQMD[16]
60 14,73   EGIA,[8] OPEC,[17] U.S. EIA[18]
59 14,503 78 U.S. Army Standard Metro[19][20]
59 14,696 60 ISO 2314, ISO 3977-2[21]
°F in Hg  % RH
70 29,92 0 AMCA,[22][23] massa jenis udara = 0,075 lbm/ft³. Standar AMCA berlaku hanya untuk udara.

Notes:

  • EGIA: Electricity and Gas Inspection Act (of Canada)
  • SATP: Standard Ambient Pressure and Temperature
  • SCAQMD: California's South Coast Air Quality Management District

Referensi[sunting | sunting sumber]

  1. ^ a b c A. D. McNaught, A. Wilkinson (1997). Compendium of Chemical Terminology, The Gold Book (ed. 2nd Edition). Blackwell Science. ISBN 0865426848. "Standard conditions for gases: Temperature, 273.15 K [...] and pressure of 105 pascals. IUPAC recommends that the former use of the pressure of 1 atm as standard pressure (equivalent to 1.01325 × 105 Pa) should be discontinued." 
  2. ^ A. D. McNaught, A. Wilkinson (1997). Compendium of Chemical Terminology, The Gold Book (ed. 2nd Edition). Blackwell Science. ISBN 0865426848. "Standard pressure: Chosen value of pressure denoted by po or p°. In 1982 IUPAC recommended the value 105 Pa, but prior to 1982 the value 101 325 Pa (= 1 atm) was usually used." 
  3. ^ NIST (1989). "NIST Standard Reference Database 7 – NIST Electron and Positron Stopping Powers of Materials Database". Diakses 08-07-25. "If you want the program to treat the material as an ideal gas, the density will be assumed given by M/V, where M is the gram molecular weight of the gas and V is the mol volume of 22414 cm3 at standard conditions (0 deg C and 1 atm)." 
  4. ^ ISO (1994), ISO 10780:1994 : Stationary source emissions - Measurement of velocity and volume flowrate of gas streams in ducts 
  5. ^ a b Robert C. Weast (Editor) (1975). Handbook of Physics and Chemistry (ed. 56th Edition). CRC Press. hlm. pp. F201–F206. ISBN 0-87819-455-X. 
  6. ^ a b "Natural gas – Standard reference conditions", ISO 13443, International Organization for Standardization, Geneva, Switzerland  ISO Standards Catalogue
  7. ^ "Extraction, First Treatment and Loading of Liquid & Gaseous Fossil Fuels", Emission Inventory Guidebook B521, Activities 050201 - 050303, September 1999, European Environmental Agency, Copenhagen, Denmark  Emission Inventory Guidebook
  8. ^ a b "Electricity and Gas Inspection Act", SOR/86-131 (defines a set of standard conditions for Imperial units and a different set for metric units)  Canadian Laws
  9. ^ "Standards of Performance for New Sources", 40 CFR--Protection of the Environment, Chapter I, Part 60, Section 60.2, 1990  New Source Performance Standards
  10. ^ "Design and Uncertainty for a PVTt Gas Flow Standard", Journal of Research of the National Institute of Standards and Technology, Vol.108, Number 1, 2003  NIST Journal
  11. ^ "National Primary and Secondary Ambient Air Quality Standards", 40 CFR--Protection of the Environment, Chapter I, Part 50, Section 50.3, 1998  National Ambient Air Standards
  12. ^ "Table of Chemical Thermodynamic Properties", National Bureau of Standards (NBS), Journal of Physics and Chemical Reference Data, 1982, Vol. 11, Supplement 2.
  13. ^ "Glossary", 2002, Compressed Air and Gas Institute, Cleveland, OH, USA  Glossary
  14. ^ a b The SI Metric System of Units and SPE Metric Standard 1984, Richardson, TX, USA (Notes for Table 2.3 on page 25 define standard cubic foot and standard cubic meter)
  15. ^ "Storage and Handling of Liquefied Petroleum Gases" and "Storage and Handling of Anhydrous Ammonia", 29 CFR--Labor, Chapter XVII--Occupational Safety and Health Administration, Part 1910, Sect. 1910.110 and 1910.111, 1993  Storage/Handling of LPG
  16. ^ "Rule 102, Definition of Terms (Standard Conditions)", Amended December 2004, South Coast Air Quality Management District, Los Angeles, California, USA  SCAQMD Rule 102
  17. ^ "Annual Statistical Bulletin", 2004, Editor-in-chief: Dr. Omar Ibrahim, Organization of the Petroleum Exporting Countries, Vienna, Austria  OPEC Statistical Bulletin
  18. ^ "Natural Gas Annual 2004", DOE/EIA-0131(04), December 2005, U.S. Department of Energy, Energy Information Administration, Washington, D.C., USA  Natural Gas Annual 2004
  19. ^ Sierra Bullets L.P. "Chapter 3 – Effects of Altitude and Atmospheric Conditions". Rifle and Handgun Reloading Manual, 5th Edition. "Effects of Altitude and Atmospheric Conditions", Exterior Ballistics Section, Sierra's "Rifle and Handgun Reloading Manual, 5th Edition", Sedalia, MO, USA  Exterior Ballistics
  20. ^ The pressure is specified as 750 mmHg. However, the mmHg is temperature dependant, as mercury expands as temperature goes up. Here the values for the 0-20 °C range are given.
  21. ^ "Gas turbines – Procurement – Part 2: Standard reference conditions and ratings", ISO 3977-2:1997 and "Gas turbines - Acceptance tests", ISO 2314:1989, Edition 2, International Organization for Standardization, Geneva, Switzerland ISO
  22. ^ ANSI/AMCA Standard 210, "Laboratory Methods Of Testing Fans for Aerodynamic Performance Rating", as implied here: http://www.greenheck.com/pdf/centrifugal/Plug.pdf when accessed on October 17, 2007
  23. ^ The standard is given as 29.92 inHg at an unspecified temperature. This most likely corresponds to a standard pressure of 101.325 kPa, converted into ~29.921 inHg at 32 °F)

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