Question

Select endothermic reaction:
a.) ${{S}^{-}}(g)+{{e}^{-}}(g)\to {{S}^{2-}}(g)$
b.) $Ne(g)+{{e}^{-}}(g)\to N{{e}^{-}}(g)$
c.) $N(g)+{{e}^{-}}(g)\to {{N}^{-}}(g)$
d.) None of these

Answer 1

Hint: Endothermic reactions have a positive value of electron gain enthalpy and energy is absorbed when an electron is added to the atom. A constant input of energy is in the form of heat and is needed to keep an endothermic reaction going.

Complete Solution :
- Endothermic reaction is a chemical reaction in which more energy is needed to break bonds in the reactants than is released when new bonds form in the products.
- Melting an ice cube, melting solid salts, thermal decomposition reaction, separating ion pairs, baking bread, and evaporating liquid water are some of the examples of endothermic reactions.
- The general equation of endothermic reaction is
\[\text{Reactants+Energy}\to \text{Products}\]

- The change in enthalpy for an endothermic reaction is always positive.
- In the reaction shown below, the reaction has a positive value of electron gain enthalpy and energy is absorbed when an electron is added to the atom.
$\begin{align}
  & Ne(g)+{{e}^{-}}(g)\to N{{e}^{-}}(g) \\
 & N(g)+{{e}^{-}}(g)\to {{N}^{-}}(g) \\
\end{align}$

- While in the following reaction, there is a negative value for electron gain enthalpy and energy is released when an electron is added to the atom making it an exothermic reaction.
${{S}^{-}}(g)+{{e}^{-}}(g)\to {{S}^{2-}}(g)$
So, the correct answer is “Option B and C”.

Note: An endothermic reaction process is a more basic term for heat absorbing phenomenon. The processes aren’t easily written as a chemical reaction. This is because the reactants do not change their chemical identity. They have a chemistry complex, also the nature of the reactants isn’t known.