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 patterns in the periodic table to explain why the substances you identified acted as the acid and the base in this reaction.
In this reaction, H2Se acts as the acid and H2O acts as the base. The conjugate acid is SeH- and the conjugate base is H3O+.
H2Se acts as the acid because it donates a proton (H+) to H2O, forming the conjugate base SeH-. H2O acts as the base because it accepts the proton, forming the conjugate acid H3O+.
In the periodic table, elements in Group 16 (also known as Group VIA) tend to act as acids by donating protons. Hydrogen selenide (H2Se) is a covalent compound that belongs to Group 16, so it can readily donate a proton in this reaction. On the other hand, water (H2O) tends to act as a base because oxygen (O) is more electronegative than selenium (Se), making it a better proton acceptor.
In this reaction, hydrogen selenide (H2Se) acts as the acid because it donates a proton (H+) to water. Water, on the other hand, acts as the base because it accepts the proton. The conjugate acid is SeH– (selenide ion) as it is formed by accepting the proton, and the conjugate base is H3O+ (hydronium ion) as it is formed by losing the proton.
The acidity or basicity of a compound can be predicted using patterns in the periodic table. In general, elements further to the right and up in the periodic table tend to be more acidic, while elements further to the left and down tend to be more basic. In this case, hydrogen selenide (H2Se), being an hydride of a nonmetal (selenium) that is on the right side of the periodic table, is acidic. Water, being a compound with oxygen (a relatively basic element), acts as the base in this reaction.