Mibvunzo Yemuenzaniso Inotsanangura Kuchinja KweEnthalpy NeEnthalpy
Enthalpy ipfungwa huru mu thermodynamics yemakemikari, inowanzo sangana nayo mumisoro yakasiyana-siyana yekemikari, kubva pakuita kwemakemikari kusvika pakuchinja kwechikamu. Muchinyorwa chino, tichaongorora mimwe mienzaniso yematambudziko uye tichakurukura shanduko dze enthalpy ne enthalpy kuti tinzwisise zviri nani pfungwa yacho.
Kunzwisisa Enthalpy
Enthalpy (H) isimba rose riri musystem yethermodynamic. Haringosanganisiri simba remukati rinochengetwa muzvikamu chete asiwo simba rinodiwa kugadzira nzvimbo yezvikamu munzvimbo yekumanikidzwa kwakapihwa. Enthalpy inoyerwa mujoules (J) muInternational System (SI).
Pamasvomhu, enthalpy inotsanangurwa se:
\[ H = U + PV \]
di mana:
– \( H \) ndiyo enthalpy
– \( U \) isimba remukati
– \( P \) kumanikidzwa
– \( V \) ivhoriyamu
Kuchinja kweEnthalpy
Kuchinja kwe enthalpy (\( \Delta H \)) kunoitika kana paine reaction yemakemikari kana physical process. Kuchinja uku kwe enthalpy kunogona kutsanangurwa sehuwandu hwekupisa hunoburitswa kana kutorwa ne system iri pa pressure yakagara iripo. Masvomhu:
\[ \Delta H = H_{\text{product}} – H_{\text{reactant}} \]
Maitiro ekunze (exothermic reactions) maitiro anoburitsa kupisa munzvimbo, uye mune aya maitiro, \( \Delta H \) haana kunaka. Panguva imwecheteyo, maitiro ekunze (endothermic reaction) maitiro anotora kupisa kubva munharaunda, uye mune aya maitiro, \( \Delta H \) ane kukosha kwakanaka.
Mibvunzo yemuenzaniso nekukurukurirana
Muenzaniso Mubvunzo 1: Kuchinja kweEnthalpy yeKupisa
Mubvunzo:
Zvinozivikanwa kuti kupiswa kwakakwana kwe 1 mole ye methane (\(CH_4\)) kunoburitsa carbon dioxide (\(CO_2\)) nemvura (\(H_2O\)). Enthalpy yedata rekuumbwa kwechinhu ndeiyi inotevera:
– \( \Delta H_{{f, H_2O (l)}} = -285.8 \text{kJ/mol} \)
– \( \Delta H_{{f, CO_2 (g)}} = -393.5 \text{kJ/mol} \)
– \( \Delta H_{{f, CH_4 (g)}} = -74.8 \text{kJ/mol} \)
Verenga shanduko ye enthalpy (\( \Delta H \)) ye combustion reaction.
Kukurukurirana:
Maitiro ekupiswa kwemethane ndeaya:
\[ CH_4 (g) + 2 O_2 (g) \museve wekurudyi CO_2 (g) + 2 H_2O (l) \]
Kuchinja kwe enthalpy kwe reaction (\( \Delta H \)) kunogona kuverengerwa uchishandisa enthalpy yekuumbwa:
\[ \Delta H = \Sigma \Delta H_f \text{products} – \Sigma \Delta H_f \text{reactants} \]
Chigadzirwa:
\[ \Delta H_f (CO_2 (g)) = -393.5 \text{kJ/mol} \]
\[ \Delta H_f (H_2O (l)) = -285.8 \text{kJ/mol} \]
Huwandu hwezvinhu zvinogadzirwa:
\[ (-393.5 \text{kJ/mol}) + 2\times(-285.8 \text{kJ/mol}) = -393.5 – 571.6 = -965.1 \text{kJ/mol} \]
Zvinoita kuti zvinhu zvisashande:
\[ \Delta H_f (CH_4 (g)) = -74.8 \text{kJ/mol} \]
\[ \Delta H_f (O_2 (g)) = 0 \text{kJ/mol} \]
(Okisijeni muchimiro chayo chakajairika ine enthalpy yekuumbwa kwe zero.)
Huwandu hwezvinhu zvinokonzeresa:
\[ (-74.8 \text{kJ/mol}) + 2\times(0 \text{kJ/mol}) = -74.8 \text{kJ/mol} \]
Saka, shanduko mu enthalpy (\( \Delta H \)) ndeiyi:
\[ \Delta H = -965.1 \zvinyorwa{kJ/mol} – (-74.8 \zvinyorwa{kJ/mol}) \]
\[ \Delta H = -965.1 + 74.8 \]
\[ \Delta H = -890.3 \text{kJ/mol} \]
Saka, shanduko ye enthalpy yekupiswa kwe 1 mole ye methane ndeye \(-890.3 \text{kJ/mol}\).
Muenzaniso Mubvunzo 2: Kuchinja kweEnthalpy muMaitiro Emuviri
Mubvunzo:
Verenga shanduko ye enthalpy kana magiramu makumi mashanu echando (\(H_2O_{(s)}\)) pa0°C anyungudutswa mumvura (\(H_2O_{(l)}\)) pa0°C. Zvinozivikanwa kuti kupisa kwekunyunguduka kwechando (\( \Delta H_{\text{fus}} \)) i6.01 kJ/mol uye huwandu hwemvura hwemolar i18 g/mol.
Kukurukurirana:
Danho rekutanga nderekuverenga huwandu hwemamota echando.
\[ \text{Moles of ice} = \frac{50 \text{g}}{18 \text{g/mol}} \approx 2.78 \text{mol} \]
Tevere tinoverenga shanduko ye enthalpy yekunyungudutsa chando:
\[ \Delta H = n \cdot \Delta H_{\text{fus}} \]
\[ \Delta H = 2.78 \text{mol} \cdot 6.01 \text{kJ/mol} \]
\[ \Delta H \inenge 16.7 \text{kJ} \]
Saka, shanduko ye enthalpy pakunyungudutsa 50 gramu yechando pa0°C inenge 16.7 kJ. Iyi inzira ye endothermic nekuti chando chinotora kupisa kuti chishanduke kuita mvura.
Muenzaniso 3: Maitiro aHess
Mubvunzo:
Shandisa mutemo waHess kuti uone shanduko ye enthalpy yemhinduro inotevera:
\[ 2 C(graphite) + 3 H_2(g) \museve wekurudyi C_2H_6(g) \]
Maitiro akati wandei anozivikanwa nekuchinja kwawo kwe enthalpy:
1. \( C(graphite) + O_2(g) \museve wekurudyi CO_2(g), \Delta H = -393.5 \chinyorwa{kJ} \)
2. \( H_2(g) + \frac{1}{2}O_2(g) \rightarrow H_2O(l), \Delta H = -285.8 \text{kJ} \)
3. \( 2 C_2H_6(g) + 7 O_2(g) \museve wekurudyi 4 CO_2(g) + 6 H_2O(l), \Delta H = -3119.6 \text{kJ} \)
Kukurukurirana:
Kuti tiverenge shanduko ye enthalpy (\( \Delta H \)) ye reaction, tinofanira kudzosera shure uye kuwanza mamwe ma reaction kuti aenderane ne target reaction.
Kurongeka:
1. Chinja maitiro \(C_2H_6 \rightarrow 2 CO_2 + 3 H_2O\):
\[2C_2H_6(g) + 7O_2(g) \museve wekurudyi 4 CO_2(g) + 6H_2O(l), \Delta H = -3119.6 \zvinyorwa{kJ}\]
Maitiro ekutendeuka nekupatsanura:
\[ 4CO_2(g) + 6H_2O(l) \museve wekurudyi 2C_2H_6(g) + 7O_2(g), \Delta H = 3119.6/2 = 1559.8 \zvinyorwa{kJ} \]
2. Mhinduro \(C \museve wekurudyi CO_2\):
\[ 4C(graphite) + 4O_2(g) \museve wekurudyi 4CO_2(g), \Delta H = 4 \nguva -393.5 = -1574 \chinyorwa{kJ} \]
3. Maitiro \(H_2\rightarrow H_2O\):
\[ 6H_2(g) + 3O_2(g) \museve wekurudyi 6H_2O(l), \Delta H = 6 \nguva -285.8 = -1714.8 \zvinyorwa{kJ} \]
Tichibatanidza zvese izvi, tinowana:
\[2C(graphite) + 3H_2(g) \museve wekurudyi C_2H_6\]
\[ \Delta H = 1559.8 – 1574 – 1714.8 = -1729 \text{kJ}\]
Saka, kuchinja kwe enthalpy kwekuita kwema moles maviri e graphite nema moles matatu e \(H_2\) kuenda ku \(C_2H_6(g)\) ndeye -1729 kJ.
Saka, kunzwisisa pfungwa ye enthalpy uye kushandiswa kwayo kumarudzi akasiyana-siyana ekuita kunoita kuti pave neruzivo rwekuti simba rinobatanidzwa sei mukuchinja kwemakemikari nemuviri. Matambudziko ari pamusoro apa mimwe mienzaniso inowanzo shandiswa muchirongwa chedzidzo kusimbisa kunzwisisa pfungwa idzi.
