Let us take another example of the reaction between two parts of hydrogen and
one part of oxygen by means of an electric spark at normal temperature and pressure. The
reaction occurs stoichiometrically according to the following chemical equation.
2H, (g) + O2(g) → 2H20 (1)
What is the role of Electric Spark in this reaction???
Answers
Electrical energy is used rather than heat energy to carry out this reaction.
Generally, evolution of heat in a reaction favours the conversion of reactants to products. However, entropy is important in determining the favourability of a reaction. Entropy is a measure of the number of ways in which energy can be distributed in any system. Entropy accounts for the fact that not all energy available in a process can be manipulated to do work.
When hydrogen and oxygen react to form water, the entropy of the products is less than that of the reactants. Offsetting this decrease in entropy, however, is the increase in entropy of the surroundings owing to the heat transferred to it by the exothermic reaction. Again because of the overall increase in entropy, the combustion of hydrogen is product-favoured.