heat added/released
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heat added/released
How do you know whether heat is added or released just by looking at the equation?
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- Posts: 97
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Re: heat added/released
I think you could find this by determining of the reaction is exothermic or endothermic reactions (endothermic reactions require a heat input). Sometimes you can tell this just by looking at the reaction. Ex. If the rxn is one reactant being broken into several products, it's probably exothermic because energy would be required to break the bonds of the larger reactant molecule.
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Re: heat added/released
It is not necessarily obvious without looking in tables for energies and enthalpies. You can try to guess by looking to see if bonds are broken and formed but you won't truly know until you calculate to see if a reaction is exothermic or endothermic.
Re: heat added/released
Forming new bonds releases energy. In a synthesis reaction where you’re forming a new product from its reactants, energy will be released because the new product is more stable. Breaking bonds requires energy. In decomposition reactions where you’re breaking apart a molecule into its simpler parts, you will need energy = endothermic. Also look at enthalpy, the sign will tell you if energy is being released (negative) or require (positive). Heat can also be directly
In the products or reactants side of the equation.
In the products or reactants side of the equation.
Re: heat added/released
If there is no delta H + or - stated in the problem then look at the products and reactants in the rxn and consider bonds being formed or broken.
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Re: heat added/released
It can also be seen if there is a phase change. If the reaction is say changing from solid to liquid or gas, then heat will be required to break the bonds so it is endothermic. If it was gas to liquid or solid, then it would be exothermic.
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