Question

For which of the following processes, enthalpy change is
positive
(a) F(g) + e⁻ →F⁻(g) (b) Cl(g) + e⁻ →Cl⁻(g)
(c)O(g)+2e⁻ →O²⁻(g) (d) H(g) + e⁻ →H⁻(g)

Answer 1

Answer:

d

Explanation:

here O ,Cl ,F are electro negative as they are small in size . F O Cl tries to be stable which 8e by accepting 1 electron

but Hydrogen will lose an electron because of its very weak electronegative force. The strength of a single proton is not enough to rip loose electrons from stronger atoms (remember hydrogen is the weakest with its single proton) such as an oxygen atom.

Answer 2

Among the following reactions, the enthalpy change positive is for the reaction

(d) H(g) + e⁻ →H⁻(g)

• Enthalpy change or Heat of the reaction : It is the amount of heat absorbed or emitted during the reaction, to form 1 mole of the product at constant pressure.
• Negative heat of reaction indicates that the reaction is exothermic.
• Positive heat of reaction indicates that the reaction is endothermic.
• Florine, Chlorine, and Oxygen  are highly electronegative elements, it is difficult to remove an electron from them, but it is easier to add one. So when an electron is added to these elements there is a release of energy, due to formation of octet structure  i.e. the reaction leads to be exothermic.
• But, Hydrogen being least electronegative ,it requires lot of energy to add an electron into it. Thus, Formation of H- is an Endothermic process.