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Scholar
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Date Posted: 7/20/2008 8:32:22 PM  Status: Closed
Need help with relative metal fire question.. asap ...
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Question Details:
 i  am really confused about the  Li (s) ..where do i get the info from

Reactive Metal Fires


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)
 

Answer:   ?
2Li(s) + CO2(g) --> Li2O(s) + CO(g)
 
Answer?
2Li(s) + 2H2O(l) --> 2LiOH(aq) + H2(g)
  Answer?


Choose which substance might be used in a fire-retarding agent for combating each of the following fires.

Choose from the following  ( water, carbon dioxide, sand silicon dioxide, carbon tetrachloride )


1.   ?    --->   sodium burning in air
2.   ?    --->   lithium burning in air
3.   ?    --->   potassium burning in air


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Answers:

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Sage
Karma Points: 3,963
Date Posted: 7/22/2008 1:29:31 AM  Status: Live
Asker's Rating: Helpful   
Response:
 
the enthalpy change for the reaction (ΔH0rxn) is calculated as
ΔH0rxn= ΣviHi[products]-ΣviHi[reactants]
from data , ΔH0f(Li (s)) = 0, ΔH0f(O2 (g))=0
a)   for the reaction
                      4Li(s)  + O2(g) -----> 2Li2O(s)
ΔH0rxn= [2 ΔH0f(Li2O(s))]-[4ΔH0f(Li (s)) +1ΔH0f(O2 (g)) ]
ΔH0rxn= [2(-597.9KJ/mol)]-[4(0)+1(0)] =  -1195.8KJ/mol
b)  for the reaction
                      2Li(s) + CO2(g) ----->Li2O(s) + CO(g)
 
ΔH0rxn= [ ΔH0f(Li2O(s))+1ΔH0f(CO(g))]-[2ΔH0f(Li (s)) +1ΔH0f(CO2 (g)) ]
 
c)   for the reaction
                      2Li(s) + 2H2O(l) -----> 2LiOH(aq) + H2(g)
 
ΔH0rxn= [2 ΔH0f(LiOH(aq))+1ΔH0f(H2 (g))]-[2ΔH0f(Li (s)) +2ΔH0f(H2O (l)) ]
substitute all the values then find ΔH0rxn

1. sodium burning in air ---------- silicon dioxide
2. lithium burning in air------------carbon dioxide
3. potassium burning in air---------carbon tetra chloride



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