Mibvunzo Yemuenzaniso Inokurukura Kuchinja KweEnthalpy Mumamiriro Ezvinhu Akajairika
Pendauluan
Kuchinja kwe enthalpy ipfungwa huru mu thermochemistry inoita basa rakakosha mumaitiro akasiyana-siyana emakemikari. Muchinyorwa chino, tichakurukura zvakadzama maitiro ekuverenga nekunzwisisa shanduko ye enthalpy pasi pemamiriro ezvinhu akajairwa kuburikidza nematambudziko akati wandei emuenzaniso uye hurukuro dzakadzama. Chinyorwa chino chinobatsira vadzidzi, vadzidzi vekoreji, uye chero ani zvake ari kudzidza chemistry kuti anzwisise zviri nani nyaya iyi.
Kunzwisisa Enthalpy uye Kuchinja Kwayo
Enthalpy (H) isimba rose rehurongwa, rine simba remukati uye simba rine chekuita nekumanikidzwa uye huwandu. Panyaya yemakemikari, tinowanzo farira shanduko ye enthalpy (ΔH), iyo inoratidza shanduko yesimba rose panguva yekuita kwesimba panguva yekumanikidzwa kwakasimba.
Kuchinja kwe enthalpy pasi pemamiriro akajairwa (ΔH⁰) ndiko kuchinja kwe enthalpy kana zvese zvinokonzeresa uye zvigadzirwa zviri mumamiriro azvo akajairwa, kureva kuti, pakumanikidzwa kwe1 atm uye tembiricha inowanzo kuve 25°C (298 K).
Mibvunzo yemuenzaniso nekukurukurirana
Mubvunzo 1: Kupisa kweMethane
Mubvunzo: Verenga shanduko ye enthalpy yakajairwa (ΔH⁰) yekupiswa kwe mole imwe ye methane (\(CH_4\)) zvichibva pane equation inotevera:
\[ CH_4(g) + 2O_2(g) \museve wekurudyi CO_2(g) + 2H_2O(l) \]
Zvinozivikanwa:
– ΔH⁰f \(CH_4(g)\) = -74.8 kJ/mol
– ΔH⁰f \(CO_2(g)\) = -393.5 kJ/mol
– ΔH⁰f \(H_2O(l)\) = -285.8 kJ/mol
Kukurukurirana:
Kuchinja kwe enthalpy kwakajairika kwemakemikari kunogona kuverengerwa uchishandisa mutemo waHess kuburikidza nefomula inotevera:
\[ \Delta H⁰ = ∑ ΔH⁰f(chigadzirwa) – ∑ ΔH⁰f(reactant) \]
Kutanga, tsvaga enthalpy yakajairika yekuumbwa kwechinhu chimwe nechimwe mukuita:
– \( ΔH⁰f_{CH_4(g)} = -74.8 \) kJ/mol
– \( ΔH⁰f_{CO_2(g)} = -393.5 \) kJ/mol
– \( ΔH⁰f_{H_2O(l)} = -285.8 \) kJ/mol (×2 yemamota maviri \(H_2O\))
Wobva waverenga huwandu hwe enthalpies yekuumbwa kwezvigadzirwa uye reactants:
\[ ∑ ΔH⁰f(chigadzirwa) = [-393.5] + [2(-285.8)]
= -393.5 + (-571.6)
= -965.1 \chinyorwa{kJ/mol} \]
\[ ∑ ΔH⁰f(reactant) = [-74.8] + [0] \]
(Makemikoro ese e elemental muchimiro chawo chekutanga ane enthalpy yakajairika yekuumbwa kwe0 kJ/mol)
Wobva waverenga shanduko ye enthalpy yakajairwa (ΔH⁰):
\[ ΔH⁰ = -965.1 – (-74.8)
= -965.1 + 74.8
= -890.3 \chinyorwa{kJ/mol} \]
Saka, shanduko yakajairika ye enthalpy yekupiswa kwe mole imwe ye methane i -890.3 kJ/mol.
Mubvunzo 2: Maitiro ekugadzira mvura
Mubvunzo: Verenga shanduko ye enthalpy (ΔH⁰) yekuumbwa kwemvura kubva kuhydrogen neokisijeni zvichibva pane zvinotevera:
\[ 2H_2(g) + O_2(g) \museve wekurudyi 2H_2O(l) \]
Zvinozivikanwa:
– ΔH⁰f \(H_2O(l)\) = -285.8 kJ/mol
Kukurukurirana:
Tinofanira kutsvaga shanduko yakajairika ye enthalpy kuti tiwane mhinduro kubva kuzvinhu zvinotanga kuenda kuzvigadzirwa zvinodiwa. Tichishandisa standard enthalpy yekuumbwa:
\[ ΔH⁰ = ∑ ΔH⁰f(chigadzirwa) – ∑ ΔH⁰f(reactant) \]
Verenga enthalpy yekuumbwa kwezvigadzirwa uye reactants:
\[
\begin{align}
∑ ΔH⁰f(chigadzirwa) & = [2(-285.8)] \\
∑ ΔH⁰f(chigadzirwa) & = -571.6 \text{ kJ/mol}
\end{align}
\]
\[
ΔH⁰f(H_2(g)) = 0 \text{ kJ/mol} \\
ΔH⁰f(O_2(g)) = 0 \text{ kJ/mol} \\
∑ ΔH⁰f(reactants) = [2(0)] + [0] = 0 \text{ kJ/mol}
\]
Wobva waverenga shanduko ye enthalpy yakajairwa (ΔH⁰):
\[ ΔH⁰ = -571.6 \chinyorwa{ kJ/mol} \]
Saka, shanduko yakajairika ye enthalpy pakuumbwa kwemvura ndeye -571.6 kJ/mol.
Mubvunzo 3: Kuora kweNitrogen Dioxide
Mubvunzo: Verenga shanduko ye enthalpy (ΔH⁰) yekuora kwe nitrogen dioxide (\(NO_2\)) kuita nitrogen monoxide gas (\(NO\)) uye oxygen gas (O₂) zvichibva pane zvinotevera:
\[ 2NO_2(g) \museve wekurudyi 2NO(g) + O_2(g) \]
Zvinozivikanwa:
– ΔH⁰f \(NO_2(g)\) = 33.2 kJ/mol
– ΔH⁰f \(NO(g)\) = 90.3 kJ/mol
Kukurukurirana:
Kuverenga kwakafanana:
\[ ΔH⁰ = ∑ ΔH⁰f(chigadzirwa) – ∑ ΔH⁰f(reactant) \]
Verenga enthalpy yekuumbwa kwechigadzirwa:
\[
\begin{align}
∑ ΔH⁰f(chigadzirwa) & = [2( ΔH⁰f_{NO(g)} )] + [ ΔH⁰f_{O_2(g)}] \\
& = [2(90.3)] + [0] \\
& = 180.6 \text{kJ/mol}
\end{align}
\]
Verenga enthalpy yekuumbwa kwema reactants:
\[
\begin{align}
∑ ΔH⁰f(reactant) & = [2( ΔH⁰f_{NO_2(g)} )] \\
& = [2(33.2)] \\
& = 66.4 \text{kJ/mol}
\end{align}
\]
Verenga shanduko yakajairika ye enthalpy (ΔH⁰):
\[ ΔH⁰ = 180.6 – 66.4 = 114.2 \text{ kJ/mol} \]
Saka, shanduko yakajairika ye enthalpy yekuora kwe nitrogen dioxide i114.2 kJ/mol.
Mhedziso
Kuverenga shanduko dze enthalpy dzakajairwa (ΔH⁰) inzira yakakosha mu thermochemistry. Nekunzwisisa mashandisirwo e enthalpies dzakajairwa dzekugadzirwa uye kushandisa mutemo waHess, tinogona kuona shanduko dzesimba mumaitiro akasiyana-siyana emakemikari. Kuburikidza nematambudziko ari pamusoro apa, vaverengi vanotarisirwa kuwana nzwisiso uye kugona kuverenga shanduko dze enthalpy dzemaitiro akasiyana-siyana emakemikari. Ruzivo urwu rwakakosha kwete chete muzvidzidzo zvedzidzo asiwo mukushandiswa kwakasiyana-siyana kwemaindasitiri uye kutsvagurudza kwesainzi.
