Ajụjụ na Mkparịta ụka gbasara nha anya Thermochemical
Thermochemistry bụ ngalaba nke kemistri nke na-amụ mgbanwe ike na-eme n'oge mmeghachi omume kemịkalụ, ọkachasị nnyefe okpomọkụ. Thermochemistry gụnyere echiche dịka enthalpy, entropy, na ike efu nke Gibbs, nke a na-eji eburu amụma ntụziaka na mberede nke mmeghachi omume. N'isiokwu a, anyị ga-enyocha ọtụtụ nsogbu atụ ma tụlee nha nha thermochemical.
Echiche Ndị Dị Mkpa nke Thermochemistry
Tupu ị banye n'ajụjụ atụ na mkparịta ụka ha, ọ dị mkpa ịmara ụfọdụ echiche bụ isi nke thermochemistry:
1. Enthalpy (H): Enthalpy bụ ụdị ike dị na sistemụ nke a na-atụ n'okpuru ọnọdụ nrụgide na-adịgide adịgide. Enwere ike ịkọwa mgbanwe dị na enthalpy (\( \Delta H \)) dị ka:
\[ \Delta H = H_{ngwaahịa} – H_{reactant} \]
2. Mmeghachi omume Endothermic na Exothermic:
– Mmeghachi omume nke mpụga okpomọkụ bụ mmeghachi omume nke na-ewepụta okpomọkụ n'ime gburugburu ebe obibi (\( \Delta H < 0 \)). - Mmeghachi omume nke endothermic bụ mmeghachi omume nke na-amịkọrọ okpomọkụ site na gburugburu ebe obibi (\( \Delta H > 0 \)).
3. Iwu Hess: Iwu Hess kwuru na mgbanwe enthalpy zuru oke nke mmeghachi omume kemịkalụ bụ otu ihe ahụ ma mmeghachi omume ahụ mere n'otu nzọụkwụ ma ọ bụ ọtụtụ nzọụkwụ. Enwere ike ịkọwa ya dị ka:
\[ \Delta H_{mkpokọta} = \Delta H_1 + \Delta H_2 + … + \Delta H_n \]
Ajụjụ na Mkparịta ụka Ihe Nlereanya
Ajụjụ Ihe atụ nke 1: Ịgbakọ Mgbanwe Enthalpy
N'ihi mmeghachi omume a:
\[ 2H_2(g) + O_2(g) \arrow aka nri 2H_2O(l) \]
Ọ bụrụ na a maara na mgbanwe enthalpy nke nhazi (\( \Delta H_f \)) nke mmiri bụ -285.8 kJ/mol. Gbakọọ mgbanwe enthalpy zuru oke maka mmeghachi omume ahụ.
Azịza:
Enwere ike ịgbakọ mgbanwe enthalpy nke mmeghachi omume (\( \Delta H_{reaction} \)) site na iji mgbanwe enthalpy nke nhazi nke ngwaahịa na ihe mmeghachi omume.
A maara:
– \[ \Delta H_f(H_2O(l)) = -285.8 \ederede{ kJ/mol} \]
Ebe ọ bụ na e mepụtara moles mmiri abụọ, mgbanwe zuru oke nke mmeghachi omume ahụ bụ:
\[ \Delta H_{mmeghachi omume} = 2(-285.8 \text{ kJ/mol}) \]
\[ \Delta H_{mmeghachi omume} = -571.6 \text{ kJ} \]
Ya mere, mgbanwe enthalpy zuru oke maka mmeghachi omume a bụ -571.6 kJ. Mmeghachi omume a bụ exothermic n'ihi na \( \Delta H \) adịghị mma.
Ajụjụ Ihe atụ nke 2: Ojiji nke Iwu Hess
N'ihi mmeghachi omume a:
\[ C(s) + O_2(g) \rightarrow CO_2(g) \hspace{2mm} \text{(1)} \]
\[ C(s) + 1/2 O_2(g) \rightarrow CO(g) \hspace{2mm} \text{(2)} \]
\[ CO(g) + 1/2 O_2(g) \rightarrow CO_2(g) \hspace{2mm} \text{(3)} \]
A maara:
– \(\Delta H_1 = -393.5 \ederede{ kJ}\)
– \(\Delta H_2 = -110.5 \ederede{ kJ}\)
Gbakọọ mgbanwe enthalpy maka mmeghachi omume (3).
Azịza:
Jiri Iwu Hess chọpụta mgbanwe enthalpy maka mmeghachi omume (3). Rịba ama na mmeghachi omume (3) nwere ike ịbụ mmeghachi omume (1) na (2):
\[ \text{Mmeghachi omume } (3): CO(g) + 1/2 O_2(g) \rightarrow CO_2(g) \]
Gbanwee mmeghachi omume (2) iji Iwu Hess:
\[ CO_2(g) \rightarrow C(s) + O_2(g) \hspace{2mm} \text{(inverse 1)}, \Delta H = +393.5 \text{ kJ} \]
\[ C(s) + 1/2 O_2(g) \rightarrow CO(g) \hspace{2mm} \text{(2)}, \Delta H = -110.5 \text{ kJ} \]
Ugbu a gbakwụnye mmeghachi omume:
\[ CO_2(g) \akara aka nri C(s) + O_2(g) + 1/2 O_2(g) \akara aka nri CO(g) + 1/2 O_2(g) \]
\[ CO_2(g) \akara aka nri C(s) + O_2(g) \akara aka nri CO(g) + 1/2 O_2(g) \]
Tinye mgbanwe enthalpy:
\[ \Delta H_{mmeghachi omume} = 393.5 – 110.5 \text{ kJ}\]
\[ \Delta H_{mmeghachi omume} = 283.0 \text{ kJ}\]
Ya mere, maka mmeghachi omume \( CO(g) + 1/2 O_2(g) \rightarrow CO_2(g) \), mgbanwe enthalpy bụ -283.0 kJ.
Ihe atụ Ajụjụ nke 3: Mmeghachi omume Kalorimeter
E nyere 100 mL nke 1.0 M hydrochloric acid (HCl) na 100 mL nke 1.0 M sodium hydroxide (NaOH). Mgbe agwakọtara ha abụọ na calorimeter, okpomọkụ na-abawanye site na 25.0 °C ruo 31.0 °C. Ọ bụrụ na ike okpomọkụ nke mmiri mmiri bụ 4.18 J/g°C na njupụta nke mmiri ahụ bụ 1.0 g/mL, gbakọọ mgbanwe enthalpy nke neutralization.
Azịza:
Langkah-langkah:
1. Gbakọọ oke nke ngwọta ahụ:
\[ \text{Mkpokọta olu} = 100 \text{ mL} + 100 \text{ mL} = 200 \text{ mL} \]
\[ \text{Mass} = 200 \text{ g} \] (n'ihi na njupụta nke ngwọta ahụ bụ 1 g/mL)
2. Gbakọọ mgbanwe okpomọkụ:
\[ \Delta T = 31.0 \ederede{ °C} – 25.0 \ederede{ °C} = 6.0 \ederede{ °C} \]
3. Gbakọọ ike nke ihe ngwọta ahụ na-amịkọrọ:
\[ q = m \cdot c \cdot \Delta T \]
\[ q = 200 \ederede{ g} \oge 4.18 \ederede{ J/g°C} \oge 6.0 \ederede{ °C} \]
\[ q = 5016 \ederede{ J} \]
\[ q = 5.016 \ederede{ kJ} \]
4. Gbakọọ mgbanwe enthalpy:
\[ \Delta H = \frac{q_{\text{solution}}}{\text{mol HCl}} \]
Ebe ọ bụ na ntụpọ nke HCl na NaOH bụ otu:
\[ \text{Moles HCl} = 1.0 \text{ M} \times 0.100 \text{ L} = 0.100 \text{ mol} \]
\[ \Delta H = \frac{5.016 \text{ kJ}}{0.100 \text{ mol}} \]
\[ \Delta H = -50.16 \ederede{ kJ/mol} \]
Ya mere, mgbanwe enthalpy maka nkwụsịtụ nke HCl na NaOH bụ -50.16 kJ/mol, nke na-egosi mmeghachi omume exothermic.
Mmechi
Thermochemistry bụ ngalaba dị mkpa nke kemistri nke na-enyere anyị aka ịghọta otu esi agbanwe ma gbanwee ike na mmeghachi omume kemịkalụ. Site n'ịghọta echiche ndị bụ isi dịka enthalpy na iwu Hess, na inwe ike itinye ha n'ọrụ na nsogbu ndị bara uru, anyị nwere ike ibu amụma mgbanwe ike nke na-eme na mmeghachi omume kemịkalụ dị iche iche. Edemede a ewepụtala ọtụtụ ihe atụ nke nsogbu ndị nwere olileanya na ha ga-enyere aka mee ka nghọta gị banyere nha nha thermochemical sikwuo ike.
