How is an endothermic reaction identified in an equation?

1 Answer
anor277
Jul 20, 2018

Well, how is an exothermic reaction represented?

Explanation:

We use the symbol #Delta# to represent heat...i.e. for a combustion reaction....

#CH_4(g) + 2O_2(g) rarr CO_2(g) + 2H_2O(l) + Delta#.

And certainly #DeltaH_"rxn"=DeltaH_"combustion of methane"#...and this could be very accurately measured. And we represent an endothermic reaction equivalently but energy appears on the left hand side as we face the equation. That is energy, #DeltaH#, is A REACTANT.

And an example of spontaneous endothermic change...the which will probably be demonstrated in your lab..

#Ba(OH)_2*8H_2O(s) + 2NH_4Cl(s) +Deltararr BaCl_2*2H_2O(s) + 2NH_3(aq) + 8H_2O (l)#

The two solids are mixed, and we get a slurry of barium salt, a whiff of ammonia gas, and the sides of the flask ice up as the entropy-driven reaction extracts heat from the surroundings...

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