Question

Write a chemical equation showing how each of the following species can behave as indicated when dissolved in water. a. \(\mathrm{HSO}_{3}^{-}\) as an acid b. \(\mathrm{CO}_{3}^{2-}\) as a base c. \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) as an acid d. \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}\) as a base

Short answer

a. \[\mathrm{HSO}_{3}^{-} + \mathrm{H_2O} \rightleftharpoons \mathrm{SO}_{3}^{2-} + \mathrm{H_{3}O}^{+}\] b. \[\mathrm{CO}_{3}^{2-} + \mathrm{H_{2}O} \rightleftharpoons \mathrm{HCO}_{3}^{-} + \mathrm{OH}^{-}\] c. \[\mathrm{H_2PO}_{4}^{-} + \mathrm{H_2O} \rightleftharpoons \mathrm{HPO}_{4}^{2-} + \mathrm{H_{3}O}^{+}\] d. \[\mathrm{C_2H_3O}_{2}^{-} + \mathrm{H_2O} \rightleftharpoons \mathrm{CH_3COOH} + \mathrm{OH}^{-}\]

Step-by-step solution

Identify the species as an acid

Since \(\mathrm{HSO}_{3}^{-}\) is labeled as an acid, it behaves as an acid in water. This means it will donate a hydrogen ion (H+) when dissolved in water.

Write the chemical equation

To write the chemical equation, we will show \(\mathrm{HSO}_{3}^{-}\) donating an H+ ion in water. This will produce bicarbonate ion (\(\mathrm{SO}_3^{2-}\)) and hydronium ion (\(\mathrm{H_3O^+}\)). Here is the balanced chemical equation: \[\mathrm{HSO}_{3}^{-} + \mathrm{H_2O} \rightleftharpoons \mathrm{SO}_{3}^{2-} + \mathrm{H_{3}O}^{+}\] #b. CO_3^{2-} as a base#

Identify the species as a base

Since \(\mathrm{CO}_{3}^{2-}\) is labeled as a base, it behaves as a base in water. This means it will accept a hydrogen ion (H+) when dissolved in water.

Write the chemical equation

To write the chemical equation, we will show \(\mathrm{CO}_{3}^{2-}\) accepting an H+ ion in water. This will produce bicarbonate ion (\(\mathrm{HCO}_{3}^{-}\)). Here is the balanced chemical equation: \[\mathrm{CO}_{3}^{2-} + \mathrm{H_{2}O} \rightleftharpoons \mathrm{HCO}_{3}^{-} + \mathrm{OH}^{-}\] #c. H_2PO_4^- as an acid#

Identify the species as an acid

Since \(\mathrm{H_2PO}_{4}^{-}\) is labeled as an acid, it behaves as an acid in water. This means it will donate a hydrogen ion (H+) when dissolved in water.

Write the chemical equation

To write the chemical equation, we will show \(\mathrm{H_2PO}_{4}^{-}\) donating an H+ ion in water. This will produce dihydrogen phosphate ion (\(\mathrm{HPO}_4^{2-}\)) and hydronium ion (\(\mathrm{H_3O^+}\)). Here is the balanced chemical equation: \[\mathrm{H_2PO}_{4}^{-} + \mathrm{H_2O} \rightleftharpoons \mathrm{HPO}_{4}^{2-} + \mathrm{H_{3}O}^{+}\] #d. C_2H_3O_2^- as a base#

Identify the species as a base

Since \(\mathrm{C_2H_3O}_{2}^{-}\) is labeled as a base, it behaves as a base in water. This means it will accept a hydrogen ion (H+) when dissolved in water.

Write the chemical equation

To write the chemical equation, we will show \(\mathrm{C_2H_3O}_{2}^{-}\) accepting an H+ ion in water. This will produce the acetic acid (\(\mathrm{CH_3COOH}\)) molecule. Here is the balanced chemical equation: \[\mathrm{C_2H_3O}_{2}^{-} + \mathrm{H_2O} \rightleftharpoons \mathrm{CH_3COOH} + \mathrm{OH}^{-}\]

Key concepts

Chemical Equations

Chemical equations are the language of chemistry, used to convey how substances react with each other. They describe the transformation of reactants into products. In an acid-base reaction, a chemical equation will show how hydrogen ions (H+) are transferred between reactants. For example, when a species behaves as an acid, it donates an H+ ion, while a base accepts one.

• The initial substances on the left side are called reactants.
• The substances formed are on the right side, known as products.
• Balancing these equations is essential to ensure the same number of each type of atom appears on both sides.

Learning how to accurately write and balance chemical equations helps in understanding the underlying chemical processes.

Dissolution in Water

When compounds dissolve in water, they interact with water molecules in specific ways. This process is crucial for understanding many acid-base reactions. For ionic compounds, dissolution results in the separation of ions.

When a substance like ext{HSO}_{3}^{-} dissolves and behaves as an acid, it donates an H+ ion to water, forming ext{SO}_3^{2-} and ext{H}_3 ext{O}^+. On the other hand, bases like ext{CO}_{3}^{2-} become more negatively charged when accepting H+ from water.

• Water acts as a solvent, separating ions and facilitating these processes.
• The process of ion separation makes the substances reactive in their respective roles, either donating or accepting hydrogen ions.

Understanding dissolution is key to predicting how substances behave in water.

Acid-Base Behavior

Acid-base behavior is a fundamental concept in chemistry that explains how substances interact with each other. An acid is a proton (H+) donor, while a base is a proton acceptor. This behavior is clearly seen in reactions involving water:

• Acids: When ext{H}_2 ext{PO}_4^{-} acts as an acid, it donates an H+ ion to water, resulting in ext{HPO}_4^{2-} and ext{H}_3 ext{O}^+.
• Bases: Contrastingly, when ext{C}_2 ext{H}_3 ext{O}_2^{-} acts as a base, it accepts an H+ ion and forms ext{CH}_3 ext{COOH} along with ext{OH}^-.

This exchange of protons is central to many chemical processes, from digestion in the human body to industrial applications. Knowing how to identify and predict these behaviors is important for any chemistry student.