# Which of the following is/are correct?

1. A

For $\mathrm{A}\left(\mathrm{g}\right)+{e}^{-}⟶{\mathrm{A}}^{-}\left(\mathrm{g}\right)\mathrm{\Delta }H$ may be negative

2. B

For ${\mathrm{A}}^{-}\left(g\right)+{e}^{-}⟶{\mathrm{A}}^{2-}\left(g\right)\mathrm{\Delta }H$ may be negative

3. C

For ${\mathrm{A}}^{-}\left(g\right)+{e}^{-}⟶{\mathrm{A}}^{2}-\left(g\right)\mathrm{\Delta }H$ must be positive

4. D

For ${\mathrm{A}}^{+3}\left(\mathrm{g}\right)+{e}^{-}⟶{\mathrm{A}}^{+2}\left(\mathrm{g}\right)\mathrm{\Delta }H$ must be negative

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### Solution:

In the case of an endothermic reaction, where the energy is drawn from the environment, the enthalpy is positive. When there is an exothermic reaction, the enthalpy is negative because energy is being released.

For $\mathrm{A}\left(\mathrm{g}\right)+{e}^{-}⟶{\mathrm{A}}^{-}\left(\mathrm{g}\right)\mathrm{\Delta }H$ may be negative as it is exothermic .

For ${\mathrm{A}}^{-}\left(g\right)+{e}^{-}⟶{\mathrm{A}}^{2}-\left(g\right)\mathrm{\Delta }H$ must be positive as it is endothermic

For ${\mathrm{A}}^{+3}\left(\mathrm{g}\right)+{e}^{-}⟶{\mathrm{A}}^{+2}\left(\mathrm{g}\right)\mathrm{\Delta }H$ must be negative as it is exothermic

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