Question

Among the following compounds, which is not an ore of magnesium?
a) Carnallite
b) Magnesite
c) Dolomite
d) Gypsum

Answer 1

Hint: We can define an ore to be a substance from which any minerals can be extracted, efficiently and economically. An ore can contain minerals of varying riches, we can find out its richness by checking which mineral and element is present in the ore. To find out which is not an ore of magnesium, we need to find out which of the options does not contain magnesium in it.

Complete step by step answer:
$1.$ We must first inspect the molecular formulas of each compound; in this way we can eliminate the compounds from our answer, which have magnesium in it, because they are automatically classified to be ores, since we know that the ore of magnesium must contain $Mg$ in its molecular formula.
$2.$ Let us look at the molecular formulas of each compound:
Carnallite: $KCl.MgCl2.6H2O$
Magnesite: $MgCO_3$
Dolomite: $MgCO_3.CaCO_3$
Gypsum: $2(CaSO4.2H2O)$
$3.$ Clearly the compound:
Carnallite contains magnesium in the form of $MgCl3$
Magnesite contains magnesium in the form of $MgCO_3$
 Dolomite contains magnesium in the form of $MgCO_3$
$4.$ In this way we can clearly see that Gypsum is the only compound that does not contain any form of magnesium in it; so we can confidently say that Gypsum is the only compound that is not an ore of Magnesium, among the given compounds.

So, the correct answer is Option d.

Note: An ore is normally found underground, that is, it has to be mined in order to be discovered. But there are certain ores which can be found even on the surface of the earth, due to weathering. The ores which are found on the surface are the ones which were originally underground, but have been displaced due to weathering. We know that weathering is when the particles of an ore once broken down, get moved because of erosion. This movement usually happens due to soil, water or even the wind.