Van der Walls sunan wani masanin kimiyyar lissafi ɗan ƙasar Holland ne, JD van der Waals (1837-1923). Lissafin yanayin van der Waals a zahiri shine lissafin yanayin iskar gas, kamar yadda daidaitaccen lissafin iskar gas na jiharBambancin shine cewa daidaitaccen lissafin iskar gas ba zai iya samar da sakamako mai kyau ba idan matsin lamba da yawan iskar gas na gaske sun isa girma. A halin yanzu, lissafin yanayin van der Waals na iya samar da sakamako mafi daidaito.
Wannan lissafin ya samo asali ne daga Van der Waals, wanda ya fahimci iyakokin lissafin gas na yanayi. Waals ya gyara lissafin gas na yanayi ta hanyar ƙara abubuwa da yawa waɗanda ke tasiri ga yanayin gas na gaske lokacin da matsin lamba da yawan gas na gaske suka yi yawa sosai.
Yayin da matsin lamba na iskar gas ke ƙaruwa, haka nan zafin jiki da yawan iskar gas ke ƙaruwa, yayin da ƙarar iskar gas ke raguwa.
Matsin iskar gas yana da daidaiton juzu'i da girma. Idan matsin iskar gas ya ƙaru, ƙarar tana raguwa. Akasin haka, idan ƙarfin iskar gas ya ragu, matsin iskar gas yana ƙaruwa. Lokacin da ƙarfin iskar gas ya ragu, yawan iskar gas yana ƙaruwa (yawa = yawa = taro / girma). Ana iya cewa matsin lamba yana da daidaiton juzu'i kai tsaye da yawa. Idan matsin iskar gas ya yi yawa, to yawan iskar gas ma yana da yawa. Akasin haka, idan matsin iskar gas ya yi ƙasa, to yawan iskar gas ma yana da ƙasa. Matsin iskar gas ma yana da daidaiton juzu'i kai tsaye da zafin jiki. Idan matsin iskar gas ya ƙaru, zafin iskar gas yana ƙaruwa. Za mu iya kammalawa cewa idan matsin iskar gas ya ƙaru, zafin iskar gas da yawa suna ƙaruwa, yayin da ƙarfin iskar gas ke raguwa.
Idan yawan iskar gas ya ragu, tazarar da ke tsakanin kwayoyin halittar tana ƙara kusantowa. Yayin da tazarar da ke tsakanin kwayoyin halittar ke ƙara kusantowa, kwayoyin halittar suna jan hankalin juna. Yana kama da lokacin da aka kusanto da wani ƙarfe zuwa ga maganadisu. Idan tazarar da ke tsakanin maganadisu da ƙarfe ta isa sosai, maganadisu ba zai iya jawo ƙarfen ba. Amma idan tazarar da ke tsakanin maganadisu da ƙarfe ta kusa, ƙarfen zai kusanto nan take. Lokacin da kwayoyin halittar suka kusa karo, electrons ɗin da ke wajen kwayoyin halittar suna korar juna (korar lantarki). Sakamakon haka, kwayoyin halittar ba za su iya mannewa tare ba. Daga wannan ɗan gajeren bayani, za a iya cewa ƙarfin jan hankali tsakanin kwayoyin halitta shi ma yana shafar yanayin iskar.
Idan matsin iskar gas ya yi yawa kuma girman iskar gas ya yi ƙanƙanta, nisan da ke tsakanin ƙwayoyin halittar yana ƙara kusantowa. A wannan yanayin, ƙwayoyin halittar suna cika kusan dukkan girman iskar gas ɗin. Domin ƙwayoyin halittar suna da girma (diamita na atomic = 10)10 m) sannan kuma muna buƙatar la'akari da girman waɗannan ƙwayoyin.
Daidaito na jiha
Van der Waals ya samo lissafin yanayi, yana la'akari da yawan kwayoyin halitta da kuma hulɗar da ke faruwa tsakanin kwayoyin halitta. Lissafin da Van der Waals ya samo asali shine gyara na daidaitaccen lissafin iskar gas na yanayin PV = nRT.
Bayani:
P = Matsin iskar gas (N/m)2 = Pa)
V = Ƙarar iskar gas (m)3)
R = Daidaiton iskar gas na duniya (R = 8,315 J/mol.K = 8315 kJ/kmol.K)
T = Zafin jiki (K)
a = Madaidaici mai ƙarfi (ƙimarsa ta dogara ne akan ƙarfin jan hankali tsakanin ƙwayoyin iskar gas)
b = ma'aunin gwaji (yana wakiltar girman mole ɗaya na ƙwayoyin iskar gas)
n = Adadin moles (mol)
bn = Jimlar adadin ƙwayoyin iskar gas
Ana samun madaidaitan a da b ta hanyar gwaji. Ƙimar madaidaitan a da b sun dogara ne akan nau'in iskar gas.
n2 /V2 = rabon murabba'in adadin moles (n) zuwa murabba'in girman gas (V). Ƙimar n2 /V2 ya dogara da matsin lamba da yawan iskar gas. Idan matsin iskar gas (P) ya yi yawa, to girman iskar gas (V) ƙarami ne. Ƙaramin V, mafi girman n2 /V2 Idan yawan iskar gas ɗin ya yi ƙanƙanta (n2 /V2 babba) to nisan da ke tsakanin kwayoyin halittar zai yi kusa. Yayin da nisan da ke tsakanin kwayoyin halittar yake kusa, to, akwai yiwuwar mu'amala tsakanin kwayoyin halittar (tana karo, tana jawo hankalin juna). Saboda haka n2 /V2 daidai yake da daidaiton a (idan aka kwatanta da lissafin van der Waals, gefen hagu). Girman ƙimar n2 /V2, mafi girman ƙarfin jan hankali tsakanin ƙwayoyin halitta (a). Akasin haka, idan matsin iskar gas (P) ƙarami ne, ƙarar iskar gas (V) zai yi girma. Mafi girman V, ƙarami n2 /V2 Ƙaramin n2 /V2 , ƙarfin jan hankali tsakanin ƙwayoyin halitta shi ma yana ƙarami.
(V – bn) = Bambanci tsakanin girman iskar gas da jimlar girman ƙwayoyin iskar gas. Madaidaici b yana nuna girman mole ɗaya na ƙwayoyin iskar gas. n = adadin ƙwayoyin. Samfurin b da n (bn) = jimlar yawan ƙwayoyin iskar gas. Idan matsin iskar gas (P) ya fi girma, girman iskar gas (V) ya fi ƙanƙanta.
Ƙaramin V, ƙarami (V – bn). Wannan yana nufin nisan da ke tsakanin kwayoyin halitta ya fi kusa kuma ba shakka ƙarfin jan hankali tsakanin kwayoyin halitta ya fi girma. Akasin haka, idan matsin iskar gas ya yi ƙasa, ƙarfin iskar gas ya fi girma. Girman iskar gas ya fi girma, mafi girma (V – bn). Mafi girma (V – bn), mafi ƙanƙantar ƙarfin jan hankali tsakanin ƙwayoyin iskar gas.
Za mu iya cewa lissafin yanayin van der Waals ya bayyana yanayin gas na gaske daidai fiye da daidaitaccen lissafin gas. Idan matsin lamba da yawan iskar gas sun yi yawa sosai, lissafin van der Waals yana ba da sakamako mafi daidaito. Idan matsin lamba na iskar gas bai yi yawa ba, to (wani2 /V2) da (V-bn) za a iya yin watsi da su, don haka lissafin Van der Waals na jihar yana canzawa zuwa daidaitaccen lissafin iskar gas na jihar.
