Hydrogens selenide (H2Se) reacts with water according to the following equation. H2Se+H2O~SeH_+H3O+ identify the acids, base, 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.

Answer 1

In the reaction between hydrogen selenide (H₂Se) and water, represented by the equation:

\[ \text{H}_2\text{Se} + \text{H}_2\text{O} \rightleftharpoons \text{SeH}^- + \text{H}_3\text{O}^+ \]

we can identify the acids, bases, and conjugate pairs as follows:

1. Acid: H₂Se

   • An acid is a substance that donates a proton (H⁺). In this reaction, H₂Se donates a proton to water, which makes it the acid.

2. Base: H₂O

   • A base is a substance that accepts a proton. In this case, water accepts a proton from H₂Se, making it the base.

3. Conjugate Base: SeH⁻

   • The conjugate base is the species that remains after the acid donates a proton. When H₂Se donates a proton, it forms SeH⁻, which is the conjugate base of H₂Se.

4. Conjugate Acid: H₃O⁺

   • The conjugate acid is the species formed when the base accepts a proton. In this reaction, when water (H₂O) accepts a proton, it turns into H₃O⁺.

Explanation Using Periodic Table Patterns

The behavior of H₂Se as an acid and H₂O as a base can be explained through their positions in the periodic table and their respective properties:

1. Hydrogen Selenide (H₂Se):

   • H₂Se is a molecule consisting of hydrogen and selenium. Selenium is in Group 16 of the periodic table, similar to sulfur (in H₂S) and oxygen (in H₂O). As you move down the group from oxygen to selenium, the acidic strength of the hydrides tends to increase. This increase is due to the larger atomic radius and lower electronegativity of selenium compared to sulfur and oxygen, making H₂Se a moderately strong acid among its group.

2. Water (H₂O):

   • Water is a very effective base because of its polar nature and ability to stabilize positive charges through hydrogen bonding. Its position in Group 16, being the most electronegative element in its group, enables it to participate effectively in acid-base reactions as a proton acceptor.

In summary, H₂Se acts as the acid by donating a proton, while H₂O acts as the base by accepting a proton. The resulting SeH⁻ is the conjugate base of H₂Se, and H₃O⁺ is the conjugate acid formed from the water. These roles are consistent with the properties and periodic trends observed for the elements involved in the reaction.