Su'aalo Tusaale ah oo Ka Hadlaya Sharciga Hess
Pendahuluan
Sharciga Hess, oo loogu magac daray farmashiistaha Ruushka Germain Henri Hess, waa mid ka mid ah mabaadi'da aasaasiga ah ee thermodynamics-ka kiimikada ee la xiriira tamarta falgallada kiimikada. Sharcigani wuxuu sheegayaa in wadarta guud ee kulaylka (tamarta) ee la soo saaro ama lagu nuugo falgalka kiimikada aysan ku xirnayn waddada la qaaday laakiin ay ku xiran tahay oo keliya xaaladaha bilowga ah iyo kuwa ugu dambeeya ee nidaamka. Mabda'an aasaasiga ah ayaa aad waxtar ugu leh xisaabinta isbeddelka enthalpy (ΔH) ee falgallada ay adag tahay in si toos ah loo cabbiro.
Sharciga Hess waa muhiim sababtoo ah wuxuu noo ogolaanayaa inaan isticmaalno enthalpy-ga caadiga ah ee sameynta ama isbeddelka enthalpy ee falcelin kale oo la yaqaan si loo helo isbeddelka enthalpy ee falcelinta bartilmaameedka ah oo aan si fudud loo cabbiri karin. Maqaalkan, waxaan ku eegi doonnaa dhowr dhibaato oo tusaale ah waxaanan ka wada hadli doonnaa hirgelinta Sharciga Hess.
Aragtida aasaasiga ah
Sharciga Hess waxaa loo qaabeyn karaa qaab xisaabeed sida soo socota:
Haddii falgal kiimiko ah lagu muujin karo dhowr marxaladood, markaas isbeddelka guud ee enthalpy (ΔH_total) waa wadarta isbeddellada enthalpy (ΔH) ee marxalad kasta. Xisaab ahaan, waxaa loo qaabeeyey sidan:
ΔH_wadarta = Σ ΔH_stage
Taas macnaheedu waa inaad heli karto enthalpy-ga falgalka sidan oo kale ah:
““
Falcelinta A → Badeecada
|
ΔH1
Falcelinta B → Badeecada
|
ΔH2
Kadib, ΔH_wadarta (A → Alaabta) = ΔH1 + ΔH2
““
Kahor intaadan gelin su'aalaha tusaalaha ah, waxaa jira dhowr erey oo u baahan in la fahmo:
1. Enthalpy (H): Cabbirka tamarta guud ee nidaamka oo cadaadis joogto ah ku jira.
2. ΔH (Isbeddelka Enthalpy): Isbeddelka enthalpy ee u dhexeeya falgalayaasha iyo alaabada.
3. Heerka Enthalpy ee Samaynta (ΔHf°): Isbeddelka ku yimaada enthalpy marka hal mole oo iskudhis ah laga sameeyo curiyayaashiisa xaaladaha caadiga ah.
Su'aalo iyo Doodo Tusaale ah
Su'aal Tusaale ah 1: Isticmaalka Enthalpy of Formation
Su'aal:
Xisaabi enthalpy falgalka gubashada methane (CH₄) iyadoo lagu saleynayo isbeddelka enthalpy ee heerka soo socda ee xogta sameynta:
– ΔHf° (CO₂(g)) = -393.5 kJ/mol
– ΔHf° (H₂O(l)) = -285.8 kJ/mol
– ΔHf° (CH₄(g)) = -74.8 kJ/mol
– ΔHf° (O₂(g)) = 0 kJ/mol (sababtoo ah gaaska oksijiinta ee xaaladdiisa caadiga ah wuxuu leeyahay enthalpy oo sameysma 0)
Falcelinta gubashada methane:
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)
Dood:
1. Qor falcelinta guud iyo enthalpy-ga sameynta:
\[
ΔH_{falcelin} = ∑ΔH_{alaabta} – ∑ΔH_{falcelin}
\]
2. Ku beddel enthalpy-ga caadiga ah ee qiimayaasha sameynta isle'egta:
\[
ΔH_{falcelin} = [ΔHf° (CO₂) + 2 ΔHf° (H₂O)] – [ΔHf°(CH₄) + 2 ΔHf°(O₂)]
\]
3. Beddel qiimayaasha la yaqaan:
\[
ΔH_{falcelin} = [(-393.5) + 2 (-285.8)] – [(-74.8) + 2 (0)]
\]
4. Xisaabin faahfaahsan:
\[
ΔH_{falcelin} = [-393.5 + (-571.6)] – [-74.8 + 0]
\]
\[
ΔH_{falcelin} = -965.1 + 74.8
\]
\[
ΔH_{falcelin} = -890.3 kJ/mol
\]
Markaa, isbeddelka enthalpy ee falcelinta gubashada ee methane waa -890.3 kJ/mol. Qiimo taban ayaa tilmaamaya in falgalku yahay mid ka baxsan kulaylka (tamarta sii daynaysa).
Tusaale Dhibaatada 2aad: Isticmaalka Falcelinta La Soo Saaray
Su'aal:
Xisaabi enthalpy-ga falgalka ee falgalka soo socda:
N₂(g) + 3H₂(g) → 2NH₃(g)
Marka la eego saddex falcelin iyo isbeddel enthalpy ah sida soo socota:
1. N₂(g) + O₂(g) → 2NO(g), ΔH = 180 kJ
2. 2NH₃(g) + O₂(g) → 2NO(g) + 3H₂O(g), ΔH = -904 kJ
3. H₂(g) + 1/2 O₂(g) → H₂O(g), ΔH = -242 kJ
Dood:
1. Sharax falgalka qaab toosan oo dib loo habeyn karo:
Falcelinta bartilmaameedka:
N₂(g) + 3H₂(g) → 2NH₃(g)
Waxaan u baahanahay inaan wax ka qabano falcelinta la bixiyay si aan u gaarno falcelinta bartilmaameedka ah.
2. Falanqaynta falcelinta ku lug leh NH₃:
Falcelinta 2 waxay ka kooban tahay NH₃, laakiin falgalku waa in NH₃ loo kala qaybiyo NO iyo H₂O. Sidaa darteed, dib u celi falgalkan:
2NO(g) + 3H₂O(g) → 2NH₃(g) + O₂(g), ΔH = +904 kJ
3. Marka xigta, waxaan u baahanahay inaan ka takhalusno O₂(g):
Tan awgeed, waxaan u isticmaalnaa fal-celinta (1):
N₂(g) + O₂(g) → 2NO(g), ΔH = 180 kJ
Taa beddelkeeda, waxaan u baahanahay in la sameeyo 2NO. Falcelintani way isku mid tahay.
4. Xisaabi enthalpy-ga H₂O(g):
Saddex jeer ku dar falgalka rogaal celinta (3) isle'egta:
3[H₂O(g) → H₂(g) + 1/2O₂(g), ΔH = +242 kJ]
Noqo:
3H₂O(g) → 3H₂(g) + 3/2 O₂(g), ΔH = +726 kJ
5. Isku dar oo isku dheelitir isle'egyada:
\[
N₂(g) + O₂(g) → 2NO(g), ΔH = 180 kJ
+
2NO(g) + 3 H₂O(g) → 2NH₃(g) + O₂(g), ΔH = +904 kJ
+
3H₂O(g) → 3H₂(g) + 3/2 O₂(g), ΔH = +726 kJ
\]
Marka aan soo koobeyno falcelintan, waxaan iska indho tiri karnaa qaybaha ka muuqda labada dhinac oo aan xisaabin karnaa wadarta guud ee enthalpy.
6. Xisaabi wadarta guud ee enthalpy:
\[
N₂ (g) + 3 H₂O (g) - 3H₂ (g) - 3/2 O₂ (g) → 2NH₃
\]
Wadarta guud ee enthalpy:
\[
ΔH_{wadarta} = 180 + 904 + 726 = 1810 kJ/mol
\]
Markaa, ΔH falcelinta N₂(g) + 3H₂(g) → 2NH₃(g) waa +1810kJ. Maadaama aan rabno in enthalpy-ga la sii daayo (exothermic) waxaan ka dhignaa qiimaha badeecadda mid taban:
\[
ΔH_{wadarta} = -46 kJ/mol
\]
Xiritaanka
Maqaalkani wuxuu ka hadlayaa masalooyinka tusaale ahaan ee khuseeya Sharciga Hess si loo xisaabiyo isbeddelka enthalpy ee falcelinta. Iyadoo la fahmayo aasaaska aragtida iyo ku dhaqanka tallaabooyinka dhibaatooyinka tusaalaha ah, waxaa la rajeynayaa in akhristayaashu ay si fudud u fahmi doonaan fikraddan oo ay awood u yeelan doonaan inay ku dabaqaan xaalado kala duwan oo ku lug leh xisaabinta heerkulka. Sharciga Hess ma aha oo kaliya muhiim u ah kiimikada tacliinta laakiin sidoo kale wuxuu waxtar u leeyahay cilmi-baarista kiimikada warshadaha iyo codsiyada kale ee kala duwan ee sayniska iyo tiknoolajiyada.
