Ajụjụ Ihe Nlereanya Na-atụle Mgbanwe Enthalpy na Enthalpy
Enthalpy bụ isi echiche na thermodynamics kemịkalụ, nke a na-ahụkarị n'ọtụtụ isiokwu kemistri, site na mmeghachi omume kemịkalụ ruo na mgbanwe nke usoro. N'isiokwu a, anyị ga-enyocha ọtụtụ nsogbu atụ ma tụlee mgbanwe enthalpy na enthalpy iji nyere anyị aka ịghọta echiche ahụ nke ọma.
Ịghọta Enthalpy
Enthalpy (H) bụ mkpokọta ike dị na sistemụ thermodynamic. Ọ gụnyere ọ bụghị naanị ike dị n'ime echekwara na obere ihe kamakwa ike dị mkpa iji mepụta oghere maka obere ihe ndị dị n'ebe nrụgide enyere. A na-atụ Enthalpy na joules (J) na Sistemụ Mba Nile (SI).
N'ime mgbakọ na mwepụ, a na-akọwa enthalpy dị ka:
\[H = U + PV \]
Ebe:
– \(H \) bụ enthalpy
– \( U \) bụ ike dị n'ime
– \( P \) bụ nrụgide
– \(V \) bụ olu
Mgbanwe Enthalpy
Mgbanwe Enthalpy (\( \Delta H \)) na-eme mgbe mmeghachi omume kemịkalụ ma ọ bụ usoro anụ ahụ mere. Enwere ike ịkọwa mgbanwe enthalpy a dị ka oke okpomọkụ ewepụtara ma ọ bụ nke sistemụ na-amịkọrọ na nrụgide na-adịgide adịgide. N'ime mgbakọ na mwepụ:
\[ \Delta H = H_{\text{product}} – H_{\text{reactant}} \]
Mmeghachi omume nke mpụga okpomọkụ bụ mmeghachi omume nke na-ewepụta okpomọkụ n'ime gburugburu ebe obibi, na mmeghachi omume ndị a, \( \Delta H \) adịghị mma. Ka ọ dị ugbu a, mmeghachi omume endothermic bụ mmeghachi omume nke na-amịkọrọ okpomọkụ site na gburugburu ebe obibi, na mmeghachi omume a, \( \Delta H \) nwere uru dị mma.
Ajụjụ na Mkparịta ụka Ihe Nlereanya
Ajụjụ Ihe Nlereanya nke 1: Mgbanwe na Enthalpy nke Ọkụ
Ajụjụ:
A maara na ọkụ zuru oke nke 1 mole nke methane (\(CH_4\)) na-emepụta carbon dioxide (\(CO_2\)) na mmiri (\(H_2O\)). Enthalpy nke data nhazi bụ dị ka ndị a:
– \( \Delta H_{{f, H_2O (l)}} = -285.8 \text{kJ/mol} \)
– \( \Delta H_{{f, CO_2 (g)}} = -393.5 \text{kJ/mol} \)
– \( \Delta H_{{f, CH_4 (g)}} = -74.8 \text{kJ/mol} \)
Gbakọọ mgbanwe enthalpy (\( \Delta H \)) nke mmeghachi omume ọkụ.
Azịza:
Mmeghachi omume ọkụ nke methane bụ:
\[ CH_4 (g) + 2 O_2 (g) \arrow CO_2 (g) + 2 H_2O (l) \]
Enwere ike ịgbakọ mgbanwe enthalpy nke mmeghachi omume (\( \Delta H \)) site na iji enthalpy nke nhazi:
\[ \Delta H = \Sigma \Delta H_f \text{products} – \Sigma \Delta H_f \text{reactants} \]
Produk:
\[ \Delta H_f (CO_2 (g)) = -393.5 \text{kJ/mol} \]
\[ \Delta H_f (H_2O (l)) = -285.8 \text{kJ/mol} \]
Mkpokọta enthalpy nke ngwaahịa:
\[ (-393.5 \text{kJ/mol}) + ugboro abụọ(-285.8 \text{kJ/mol}) = -393.5 – 571.6 = -965.1 \text{kJ/mol} \]
Ihe ndị na-emeghachi omume:
\[ \Delta H_f (CH_4 (g)) = -74.8 \text{kJ/mol} \]
\[ \Delta H_f (O_2 (g)) = 0 \text{kJ/mol} \]
(Oxygen n'ọnọdụ nkịtị ya nwere enthalpy nke e guzobere efu.)
Mkpokọta enthalpy nke ihe mmeghachi omume:
\[ (-74.8 \text{kJ/mol}) + ugboro abụọ(0 \text{kJ/mol}) = -74.8 \text{kJ/mol} \]
Ya mere, mgbanwe dị na enthalpy (\( \Delta H \)) bụ:
\[ \Delta H = -965.1 \ederede{kJ/mol} – (-74.8 \ederede{kJ/mol}) \]
\[ \ Delta H = -965.1 + 74.8 \]
\[ \Delta H = -890.3 \ederede{kJ/mol} \]
Ya mere, mgbanwe enthalpy maka ọkụ nke 1 mole nke methane bụ \(-890.3 \text{kJ/mol}\).
Ajụjụ Ihe Nlereanya nke 2: Mgbanwe Enthalpy na Usoro Ahụ
Ajụjụ:
Gbakọọ mgbanwe enthalpy mgbe gram 50 nke ice (\(H_2O_{(s)}\)) na 0°C gbazere ka ọ ghọọ mmiri (\(H_2O_{(l)}\)) na 0°C. A maara na okpomọkụ nke agbaze nke ice (\( \Delta H_{\text{fus}} \)) bụ 6.01 kJ/mol na oke molar nke mmiri bụ 18 g/mol.
Azịza:
Nzọụkwụ mbụ bụ ịgbakọ ọnụọgụ nke ice.
\[ \text{Moles of ice} = \frac{50 \text{g}}{18 \text{g/mol}} \approx 2.78 \text{mol} \]
Ọzọ, anyị na-agbakọ mgbanwe enthalpy maka ịgbaze ice:
\[ \Delta H = n \cdot \Delta H_{\text{fus}} \]
\[ \Delta H = 2.78 \text{mol} \cdot 6.01 \text{kJ/mol} \]
\[ \Delta H \ihe dịka 16.7 \text{kJ} \]
Ya mere, mgbanwe enthalpy mgbe agbaze gram 50 nke ice na 0°C bụ ihe dị ka 16.7 kJ. Nke a bụ usoro endothermic n'ihi na ice na-amịkọrọ okpomọkụ iji ghọọ mmiri.
Ihe atụ nke 3: Mmeghachi omume Hess
Ajụjụ:
Jiri iwu Hess chọpụta mgbanwe enthalpy maka mmeghachi omume ndị a:
\[ 2 C(graphite) + 3 H_2(g) \rightarrow C_2H_6(g) \]
A maara ọtụtụ mmeghachi omume na mgbanwe enthalpy ha:
1. \( C(graphite) + O_2(g) \rightarrow CO_2(g), \Delta H = -393.5 \text{kJ} \)
2. \( H_2(g) + \frac{1}{2}O_2(g) \rightarrow H_2O(l), \Delta H = -285.8 \text{kJ} \)
3. \( 2 C_2H_6(g) + 7 O_2(g) \nriaka 4 CO_2(g) + 6 H_2O(l), \Delta H = -3119.6 \text{kJ} \)
Azịza:
Iji gbakọọ mgbanwe enthalpy (\( \Delta H \)) nke mmeghachi omume ahụ, anyị kwesịrị ịtụgharị ma mụbaa ụfọdụ mmeghachi omume ahụ iji kwekọọ na mmeghachi omume ebumnuche.
Langkah-langkah:
1. Gbanwee mmeghachi omume \(C_2H_6 \rightarrow 2 CO_2 + 3 H_2O\):
\[2C_2H_6(g) + 7O_2(g) \rightarrow 4 CO_2(g) + 6H_2O(l), \Delta H = -3119.6 \ederede{kJ}\]
Gbanwee ma kewaa mmeghachi omume:
\[ 4CO_2(g) + 6H_2O(l) \ aka nri 2C_2H_6(g) + 7O_2(g), \Delta H = 3119.6/2 = 1559.8 \ederede{kJ} \]
2. Mmeghachi omume \(C \rightarrow CO_2\):
\[ 4C(graphite) + 4O_2(g) \rightarrow 4CO_2(g), \Delta H = ugboro anọ -393.5 = -1574 \text{kJ} \]
3. Mmeghachi omume \(H_2\rightarrow H_2O\):
\[ 6H_2(g) + 3O_2(g) \rightarrow 6H_2O(l), \Delta H = 6 \ ugboro -285.8 = -1714.8 \ederede {kJ} \]
Ijikọta ya niile, anyị ga-enweta:
\[2C(graphite) + 3H_2(g) \ aka nri C_2H_6 \]
\[ \Delta H = 1559.8 – 1574 – 1714.8 = -1729 \text{kJ}\]
Ya mere, mgbanwe enthalpy nke mmeghachi omume nke moles abụọ nke graphite na moles atọ nke \(H_2\) na \(C_2H_6(g)\) bụ -1729 kJ.
Ya mere, nghọta nke echiche nke enthalpy na ojiji ya na ụdị mmeghachi omume dị iche iche na-enye nghọta banyere otu ike si etinye aka na mgbanwe kemịkalụ na anụ ahụ. Nsogbu ndị dị n'elu bụ ụfọdụ ihe atụ a na-ejikarị eme ihe na usoro ọmụmụ iji mee ka nghọta nke echiche ndị a sikwuo ike.
