Correct Answer - Option 4 : Ferrous Oxide
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Seawater, water that makes up the oceans and seas, covering more than 70 per cent of Earth’s surface. Seawater is a complex mixture of 96.5 per cent water, 2.5 per cent salts, and smaller amounts of other substances, including dissolved inorganic and organic materials, particulates, and a few atmospheric gases.
- Seawater constitutes a rich source of various commercially important chemical elements. Much of the world’s magnesium is recovered from seawater, as are large quantities of bromine. In certain parts of the world, sodium chloride (table salt) is still obtained by evaporating seawater. Magnesium is present in seawater in amounts of about 1300 ppm. After sodium, it is the most commonly found cation in oceans.
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Calcium is one of the most common elements found in seawater. Inputs of dissolved calcium (Ca2+) to the ocean include the weathering of calcium sulfate, calcium silicate, and calcium carbonate, basalt-seawater reaction, and dolomitization
- Seawater contains approximately 400 ppm calcium. One of the main reasons for the abundance of calcium in water is its natural occurrence in the earth's crust.
NOTE- Ferrous oxide, commonly known as iron(II) oxide contains iron that lost 2 elections in the oxidation process. So it is able to bond with other atoms that have an extra 2 electrons to share. Iron(III) oxide is insoluble in water but dissolves readily in strong acid, e.g. hydrochloric and sulfuric acids. It is not found in Oceans.
