Question

Which ion makes up 7.7 percent of the ions in seawater? A. calcium C. chloride B. sulfate D. sodium

Short answer

The ion that makes up 7.7% of ions in seawater is sulfate (B).

Step-by-step solution

Understand the question

The question asks us to identify the ion that makes up 7.7% of the ions present in seawater. This involves knowing the composition of ions in seawater to determine the correct answer.

Recall common ions in seawater

Seawater primarily consists of several ions, with the major ones being chloride (Cl⁻), sodium (Na⁺), sulfate (SO₄²⁻), and calcium (Ca²⁺). These ions vary in their proportions.

Know the proportions of seawater ions

In typical seawater, the proportion of ions is usually around: 55% chloride, 30.6% sodium, 7.7% sulfate, and 1.2% calcium. These percentages help in identifying the correct ion.

Identify the ion matching 7.7%

Based on the proportions, sulfate (SO₄²⁻) makes up 7.7% of the ions in seawater.

Key concepts

Sulfate Ion

Sulfate ions, represented as \( \text{SO}_4^{2-} \), are one of the significant components of seawater. These ions are remarkable because they are the third most abundant in seawater, constituting about 7.7% of all ions, which is crucial information when analyzing the chemical composition of seawater.
Sulfate ions play several vital roles in marine chemistry and biology:

• They participate in the sulfur cycle, an essential ecological process.
• They can affect the alkalinity of seawater, helping to regulate its pH balance.
• In combination with calcium ions, they form calcium sulfate, which can precipitate under specific conditions.

Understanding sulfate ions helps us better grasp marine ecosystems' intricate balance and the chemical processes taking place in the ocean.

Chloride Ion

Chloride ions, denoted as \( \text{Cl}^- \), dominate the ionic composition of seawater. They account for about 55% of the ions, making them the most abundant. This high concentration is due to chloride's essential role in maintaining the ocean's salinity.
The importance of chloride ions can be seen in several areas:

• They are a key determinant of the overall salinity level of oceans, which influences oceanic currents and marine life habitats.
• Chloride ions are involved in various biochemical processes, serving as stabilizers for enzyme activities in marine organisms.
• These ions contribute to the osmotic balance within aquatic organisms.

When considering the high abundance of chloride ions, their significance in marine chemistry and biological functions becomes crystal clear.

Sodium Ion

Sodium ions, represented by \( \text{Na}^+ \), are also a vital part of seawater's ionic composition. They comprise around 30.6% of the seawater ion content, reflecting their importance in the marine environment.
Sodium ions are crucial for a number of reasons:

• They help to maintain seawater's electrical neutrality in combination with chloride ions.
• Sodium plays essential roles in marine organisms, especially in nerve function and maintaining fluid balance.
• It is also involved in chemical processes like the sodium-potassium pump, fundamental for cellular functions in marine life.

These ions, together with chloride, largely define the salinity and overall ionic balance of the ocean.

Calcium Ion

Calcium ions, indicated as \( \text{Ca}^{2+} \), are present in smaller quantities in seawater, making up approximately 1.2% of the ionic composition. Despite their lower proportion, calcium ions play pivotal roles in marine chemistry and ecosystems.
Key functions of calcium ions in the ocean include:

• Participating in the formation of shells and skeletons of marine organisms, like corals and mollusks, through the process of biomineralization.
• Regulating the hardness of seawater, which can influence the availability of other ions.
• Interacting with carbonate ions to create calcium carbonate, which is crucial for marine life structures.

The presence of calcium ions is essential for living marine organisms and maintaining oceanic chemical equilibria.