Get Exothermic Reaction essential facts below. View Videos or join the Exothermic Reaction discussion. Add Exothermic Reaction to your PopFlock.com topic list for future reference or share this resource on social media.
Chemical reaction that releases energy as light or heat
An exothermic thermite reaction using iron(III) oxide. The sparks flying outwards are globules of molten iron trailing smoke in their wake.
Expressed in a chemical equation: reactants -> products + energy.
Exothermic Reaction means "exo" (derived from the greek word: "", literally translated to "out") meaning releases and "thermic" means heat. So the reaction in which there is release of heat with or without light is called
An exothermic reaction is a chemical reaction that releases heat. It gives net energy to its surroundings. That is, the energy needed to initiate the reaction is less than the energy released.
When the medium in which the reaction is taking place collects heat, the reaction is exothermic.
When using a calorimeter, the total amount of heat that flows into (or through) the calorimeter is the negative of the net change in energy of the system.
The absolute amount of energy in a chemical system is difficult to measure or calculate. The enthalpy change, ?H, of a chemical reaction is much easier to work with. The enthalpy change equals the change in internal energy of the system plus the work needed to change the volume of the system against constant ambient pressure. A bomb calorimeter is very suitable for measuring the energy change, ?H, of a combustion reaction. Measured and calculated ?H values are related to bond energies by:
?H = (energy used in forming product bonds) - (energy released in breaking reactant bonds)
where ?H298.15 K is the standard enthalpy of reaction at 298 K, T0 and T1 are the initial and final temperature of the system, respectively, and Cp,p and Cp,r are the heat capacities of the product and reactant, respectively.
Assuming the heat capacity of the system remains as a constant value Cp,p=Cp,r=Cp, the change of temperature ?T=T1−T0 can be expressed as
The conceptually related endotherm and ectotherm (or sometimes exotherm) are concepts in animal physiology.
In quantum numbers, when any excited energy level goes down to its original level for example: when n=4 fall to n=2, energy is released so, it is exothermic.
Where an exothermic reaction causes heating of the reaction vessel which is not controlled, the rate of reaction can increase, in turn causing heat to be evolved even more quickly. This positive feedback situation is known as thermal runaway. An explosion can also result from the problem.
Heat production or absorption in either a physical process or chemical reaction is measured using calorimetry. One common laboratory instrument is the reaction calorimeter, where the heat flow into or from the reaction vessel is monitored. The technique can be used to follow chemical reactions as well as physical processes such as crystallization and dissolution.
Energy released is measured in Joule per mole. The reaction has a negative ?H(heat change) value due to heat loss.
e.g.: -123 J/mol
^ abYin, Xi; Wu, Jianbo; Li, Panpan; Shi, Miao; Yang, Hong (January 2016). "Self-Heating Approach to the Fast Production of Uniform Metal Nanostructures". ChemNanoMat. 2 (1): 37-41. doi:10.1002/cnma.201500123.