Is this reaction likely to be spontaneous? 2Li(s) + 2H2O(g) ----> 2LiOH(s) + H2(g) ΔH = -222 kJ
1 Answer
Yes it would be spontaneous for temperatures less than about 5000 K
To determine if a reaction is spontaneous or not, one needs to consider the enthalpy
The Gibbs free energy equation combines these two values along with temperature to produce a
Temperature (in Kelvin) has an effect : this is summarized in the table below - DH is
In this case you are not given
The technical answer depends on if the entropy is increasing in the reaction (a positive
The
You can tell from many reactions just by looking if disorder (entropy) is increasing. In this case, it is not so clear so I did a calculation. The calculation looks like
This is a decrease in entropy and unfavorable toward spontanaeity
Since both
You are not given the temperature but the lithium is reacting with steam which is at minimum 373 K (100 degrees Celsius)
At this temperature
This is spontaneous. (the
Note as the temperature increases, the situation changes. At about 5000 K, the reaction would cease to be spontaneous
Source of table : http://www.sparknotes.com/testprep/books/sat2/chemistry/chapter9section7.rhtml