In the reaction \( H_2Se + H_2O \rightarrow SeH^- + H_3O^+ \), hydrogen selenide \( (H_2Se) \) acts as an acid because it donates a proton \( (H^+) \) to water \( (H_2O) \), which acts as a base. The water molecule, being a polar molecule with a significant electronegativity (due to oxygen), has the ability to accept a proton, making it a suitable base in this context. The hydronium ion \( (H_3O^+) \) formed is the conjugate acid of water, while the selenide ion \( (SeH^-) \) is the conjugate base of hydrogen selenide. The electronegativity of oxygen in water allows it to stabilize the positive charge when it gains a proton, while the relatively less electronegative selenium in \( H_2Se \) facilitates its role as a proton donor in this acid-base reaction.
Use the periodic table to complete the activity.
An illustration shows the periodic table of elements with elements arranged in increasing order of atomic number in 18 columns (groups) and 7 rows (periods). The electronegativity of elements increases from left to right, across a period. The hydrogen on the left is included in group with medium electronegativity. Also, fluorine is shown as element with highest electronegativity.
Hydrogen selenide ( H2Se ) reacts with water according to the following equation.
H2Se+H2O→SeH−+H3O+
In three to five sentences, identify the acid, base, conjugate acid, and conjugate base in this reaction. Use the periodic table to explain why each substance acted as the acid or the base in this reaction.
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