Question

Write the formulas and names of three different polyprotic acids.

Short answer

Three examples of polyprotic acids are sulfuric acid (\(H_2SO_4\)), carbonic acid (\(H_2CO_3\)), and phosphoric acid (\(H_3PO_4\)).

Step-by-step solution

Select the first polyprotic acid

Let's begin with a diprotic acid, sulfuric acid. Its formula is \(H_2SO_4\). It can donate two protons per molecule to an aqueous solution.

Select the second polyprotic acid

Next, consider carbonic acid, which is also a diprotic acid. Its formula is \(H_2CO_3\). It can donate two protons per molecule to the aqueous solution similarly to sulfuric acid.

Select the third polyprotic acid

Finally, let's choose phosphoric acid. It is a triprotic acid and its formula is \(H_3PO_4\). This acid can donate three protons per molecule to an aqueous solution.

Key concepts

Sulfuric Acid

Sulfuric acid is one of the most well-known and widely used acids in the world. Its chemical formula is \( H_2SO_4 \), and it is classified as a diprotic acid. This means it can donate two protons (hydrogen ions) when dissolved in a solution.

As one of the strongest acids available, sulfuric acid completely dissociates in water, releasing hydrogen ions and sulfate ions \((SO_4^{2-})\). The complete dissociation makes it a strong acid, which is why it's frequently used in industry for processes ranging from fertilizer production to wastewater treatment.

The two-step dissociation process for sulfuric acid involves the following reactions:

• First dissociation: \( H_2SO_4 \rightarrow H^+ + HSO_4^- \)
• Second dissociation: \( HSO_4^- \rightarrow H^+ + SO_4^{2-} \)

These steps show how the molecule discharges its two protons. Remember to handle sulfuric acid carefully, as it is highly corrosive.

Carbonic Acid

Carbonic acid \( H_2CO_3 \) is a weaker diprotic acid formed in solution when carbon dioxide is dissolved in water. This characteristic makes it crucial in regulating the pH of blood and other biological systems.

In an aqueous environment, carbonic acid partially dissociates into bicarbonate \((HCO_3^- )\) and carbonate \((CO_3^{2-})\) ions. The two steps in its dissociation are:

• First dissociation: \( H_2CO_3 \rightarrow H^+ + HCO_3^- \)
• Second dissociation: \( HCO_3^- \rightarrow H^+ + CO_3^{2-} \)

Unlike sulfuric acid, carbonic acid's dissociation is not complete, which results in it behaving as a weaker acid. It plays a vital role in buffering systems in nature, maintaining a stable pH in blood and other biological fluids.

Phosphoric Acid

Phosphoric acid is a triprotic acid with the formula \( H_3PO_4 \). It can donate up to three protons when in an aqueous solution, making it an important acid in both chemistry and biology.

The dissociation of phosphoric acid occurs in three stages, corresponding to the release of its three protons:

• First dissociation: \( H_3PO_4 \rightarrow H^+ + H_2PO_4^- \)
• Second dissociation: \( H_2PO_4^- \rightarrow H^+ + HPO_4^{2-} \)
• Third dissociation: \( HPO_4^{2-} \rightarrow H^+ + PO_4^{3-} \)

This multi-step dissociation means phosphoric acid is versatile, providing different levels of acidity depending on the amount of dissociation.

Phosphoric acid is commonly used in food additives (such as colas) and fertilizers, and it's a key component in cleaning products. Its ability to donate several protons makes it effective in various chemical applications.