Name: how real gases deviate from ideal behavior
Uploaded: 2025-05-22T09:05:49.000Z
Duration: 1 min 10 s
Channel: JoVE

İdeal gaz denkleminin iki önemli dezavantajı vardır: birincisi, gaz moleküllerinin hacmini dikkate almaz ve ikincisi, gaz molekülleri arasındaki çekici moleküller arası kuvvetleri hesaba katmaz. 
Gaz n sayıda mol içeriyorsa ve bunların her biri b hacmini işgal ediyorsa, gaz moleküllerinin kapladığı toplam hacim nb'dir. Böylece, gaz moleküllerinin hareket etmesi için mevcut hacim, toplam hacim eksi nb olacaktır.
Çekici moleküller arası kuvvetler, molar yoğunluğun karesiyle orantılı basıncı azaltır. Çekici moleküller arası kuvvetlerin yokluğunda, aynı nRT'ye ulaşmak için daha yüksek basınç gerekir.
Bu, ideal gaz denkleminin dezavantajlarını ele almaya çalışan van der Waals durum denklemidir. Burada, a ve b, incelenen gazın türüne bağlı olan ampirik sabitlerdir.
Van der Waals denklemi, sıvıdan buhara geçiş ve Joule-Thomson etkisi gibi gerçek gazın davranışını yeterince tahmin eder.

<ol>
	<li>Genç, H.D. ve Freedman, R.A. (2012). Modern Fizik ile Üniversite Fiziği. San Francisco, Kaliforniya: Pearson; Bölüm 18.1; sayfa 595 ve 617.</li>
	<li>Stax'ı açın. (2019). Üniversite Fiziği Cilt 2. [Web sürümü]. <a href="https://openstax.org/details/books/university-physics-volume-2">https://openstax.org/details/books/university-physics-volume-2 adresinden alındı</a>; Bölüm 2.1; Sayfa 75.</li>
</ol>

van der waals denklemi

Van der Waals Equation

İdeal gaz yasası, yüksek sıcaklıklarda ve düşük basınçlarda iyi çalışan bir yaklaşımdır. Van der Waals durum denklemi (Hollandalı fizikçi Johannes van der Waals, 1837-1923'ten sonra adlandırıldı) iki faktörü dikkate alarak onu iyileştirir.

İlk olarak, moleküller arasındaki çekici kuvvetler, daha yüksek yoğunluklarda daha güçlü olan ve basıncı azaltan kuvvetler, basınca, mol yoğunluğunun karesiyle çarpılan bir pozitif bir katsayı olan "a" ile eklenerek dikkate alınır. İkinci olarak, moleküllerin hacmi, bir maddenin birim molekül hacmi olarak düşünülebilecek pozitif bir sabit "b" ile temsil edilir. Bu, moleküllerin hareket edebilecekleri kalan hacmi vermek için toplam hacimden çıkarılır. Sabitler "a" ve "b" her bir gaz için deneysel olarak belirlenir. Elde edilen denklem şöyledir:

<img alt="Equation1" src="/files/ftp_upload/13668/13668_Equation_1.svg" style="text-align: center; height: 30px;" />

Karbondioksit gazı için van der Waals denklemi, sabit "a" 0,364 J·m3/mol2 ve sabit "b" ise 4,27 x 10−5 m3/mol. Eğer bu gazın 1 molü 300 cm3 hacme sıkıştırılırsa ve 300 K sıcaklıkta tutulursa, gazın basıncı van der Waals denklemi kullanılarak hesaplanabilir. Basıncın van der Waals denklemine göre yeniden düzenlenmesi

<img alt="Equation2" src="/files/ftp_upload/13668/13668_Equation_2.svg" style="text-align: center; height: 30px;" />

ve bilinen miktarların yerine konmasıyla,

<img alt="Equation3" src="/files/ftp_upload/13668/13668_Equation_3.svg" style="text-align: center; height: 32px;" />

Karbondioksit gazının basıncı

<img alt="Equation4" src="/files/ftp_upload/13668/13668_Equation_4.svg" style="text-align: center; height: 16px;" />

Düşük yoğunluk sınırlamasında (küçük "n"), "a" ve "b" terimleri ihmal edilebilir ve van der Waals denklemi ideal gaz yasasına indirgenir. Öte yandan, van der Waals denkleminin ikinci terimi küçükse, yani moleküller birbirine çok yakınsa, o zaman basınç aynı "nRT" değerini elde etmek için daha yüksek olmalıdır, çok sıkıştırılmış bir gaz durumunda beklenen budur. Bununla birlikte, basınçtaki artış, argümanın önerdiğinden daha azdır çünkü yüksek yoğunluklarda, van der Waals denkleminin basınç düzeltme terimi önemlidir. Basınç düzeltme terimi pozitif olduğundan, aynı "nRT" değerini elde etmek için daha düşük bir basınç gerektirir. Van der Waals durum denklemi, sıvı-gaz faz geçişlerini tahmin etmek gibi çeşitli koşullar altında çoğu gaz için iyi çalışır.

Van der Waals Denklemi

İdeal gaz yasası, yüksek sıcaklıklarda ve düşük basınçlarda iyi çalışan bir yaklaşımdır. Van der Waals devlet denklemi (adını Hollandalılardan almıştır ...

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JoVE Core

Physics

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Unit 1

Ünite 1

The Kinetic Theory of Gases

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KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

how real gases deviate from ideal behavior

Real gases often deviate from the ideal gas law, especially at low temperatures and high pressures. The van der Waals equation improves the ideal gas model by adding two corrections that account for these real-world effects.

One correction accounts for attractive forces between molecules. These forces become stronger at higher densities and lower the measured pressure, so the equation adds a pressure term based on the square of the molar density and a positive constant a.

The second correction accounts for the space occupied by the molecules themselves. A positive constant b represents the volume of the molecules, or the volume of a mole of molecules, and this amount is subtracted from the total volume to leave the space the gas can actually move in. The values of a and b are found experimentally for each gas.

For carbon dioxide, the van der Waals constants are a = 0.364 J·m3/mol2 and b = 4.27 x 10−5 m3/mol. If 1 mole of carbon dioxide is confined to 300 cm3 at 300 K, the pressure can be calculated by rearranging the van der Waals equation for pressure and substituting the known values.

At low density, the a and b terms are small, so the van der Waals equation reduces to the ideal gas law. At very high density, the molecules are close together, so a higher pressure is needed to reach the same nRT. Even then, the pressure increase is smaller than a simple compression argument suggests because the pressure correction term becomes significant. This makes the van der Waals equation useful for many gases, including cases that involve liquid-gas phase transitions.

How Real Gases Deviate from Ideal Behavior

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How Real Gases Deviate from Ideal Behavior | JoVE K12

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How Real Gases Deviate from Ideal Behavior

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