Arrange the soluble cations present in seawater in decreasing order of their concentration:
(A) Mg2+ (B) Na+ (C) Ca2+ (D) K+ (E) Sr2+
Choose the correct answer from the options given below:

Correct option is C

The concentrations of soluble cations in seawater in decreasing order are: Sodium (Na+) > Magnesium (Mg2+) > Potassium (K+) > Calcium (Ca2+) > Strontium (Sr2+).
This order is based on their relative abundances in seawater:
1. Sodium (Na+): The most abundant cation in seawater.
2. Magnesium (Mg2+): The second most abundant cation, essential for marine chemistry.
3. Potassium (K+): Present in moderate amounts compared to calcium.
4. Calcium (Ca2+): Slightly less abundant than potassium but important for marine organisms.
5. Strontium (Sr2+): Present in trace amounts and less abundant than all other cations listed.
Thus, the correct order is (B), (A), (D), (C), (E), making option (c) the right answer.
Information Booster: 1. Seawater composition is dominated by sodium and chloride ions, contributing significantly to salinity.
2. Magnesium, the second most abundant cation, influences seawater alkalinity and biological processes.
3. Potassium and calcium play vital roles in marine ecosystems, with potassium being slightly more concentrated than calcium.
4. Strontium exists in trace amounts and is used as a geochemical tracer in studies of ocean circulation and paleoclimate.
5. The relative abundances of these cations are consistent due to the stability of the ocean's chemical composition over time.
6. Variations in local seawater composition can occur due to factors like evaporation, precipitation, and biological activity.