In the chemistry lab, one often has to work with very reactive metals such as sodium and lithium. Unfortunately, these same metals can react vigorously with water or oxygen and cause fires. Given the following information:
delta Hfo (kJ/mol) delta Hfo (kJ/mol)
Li2O(s) -597.9 Li (aq) -278.5
Na2O(s) -416 Na (aq) -240
K2O(s) -361 K (aq) -251
CO(g) -110.5 CO2(g) -393.5
H2O(l) -286 OH-(aq) -230
CCl4(l) -135 SiO2(s) -911
LiCl(s) -409 NaCl(s) -411
KCl(s) -436 Cl-(aq) -167
Calculate delta H0 for the following reactions:
4 Li(s) O2(g) --> 2 Li2O(s)
2Li(s) CO2(g) --> Li2O(s) CO(g)
2Li(s) 2H2O(l) --> 2LiOH(aq) H2(g)
Choose which substance might be used in a fire-retarding agent for combating each of the following fires.
potassium burning in air
sodium burning in air
lithium burning in air
Reactive Metal Fires?
2017-01-10 5:11 pm
回答 (1)
2017-01-10 6:02 pm
(1)
4 Li(s) + O₂(g) → 2 Li₂O(s) …. ΔH°
ΔH° = 2 ΔHf°[Li₂O(s)] - 4 ΔHf°[Li(s)] - ΔHf°[O₂]
= [2 × (-597.9) - 4 × 0 - 0] kJ
= -1195.8 kJ
====
(2)
2Li(s) + CO₂(g) → Li₂O(s) + CO(g) …. ΔH°
ΔH° = ΔHf°[Li₂O(s)] + ΔHf°[CO(g)]- 2 ΔHf°[Li(s)] - ΔHf°[CO₂(g)]
= [(-597.9) + (-110.5) - 2 × 0 - (-393.5)] kJ
= -314.9 kJ
====
(3)
2Li(s) + 2H₂O(l) → 2 Li⁺(aq) + 2 OH⁻(aq) + H₂(g) …. ΔH°
ΔH° = 2 ΔHf°[Li⁺(aq)] + 2 ΔHf°[OH⁻(aq)] + ΔHf°[H₂(g)]- 2 ΔHf°[Li(s)] - 2 ΔHf°[H₂O(l)]
= [2 × (-278.5) + 2 × (-230) + 0 - 2 × 0 - 2 × (-286)] kJ
= -445 kJ
4 Li(s) + O₂(g) → 2 Li₂O(s) …. ΔH°
ΔH° = 2 ΔHf°[Li₂O(s)] - 4 ΔHf°[Li(s)] - ΔHf°[O₂]
= [2 × (-597.9) - 4 × 0 - 0] kJ
= -1195.8 kJ
====
(2)
2Li(s) + CO₂(g) → Li₂O(s) + CO(g) …. ΔH°
ΔH° = ΔHf°[Li₂O(s)] + ΔHf°[CO(g)]- 2 ΔHf°[Li(s)] - ΔHf°[CO₂(g)]
= [(-597.9) + (-110.5) - 2 × 0 - (-393.5)] kJ
= -314.9 kJ
====
(3)
2Li(s) + 2H₂O(l) → 2 Li⁺(aq) + 2 OH⁻(aq) + H₂(g) …. ΔH°
ΔH° = 2 ΔHf°[Li⁺(aq)] + 2 ΔHf°[OH⁻(aq)] + ΔHf°[H₂(g)]- 2 ΔHf°[Li(s)] - 2 ΔHf°[H₂O(l)]
= [2 × (-278.5) + 2 × (-230) + 0 - 2 × 0 - 2 × (-286)] kJ
= -445 kJ
收錄日期: 2021-04-18 15:58:49
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20170110091105AAsYHFu