Question

Which of the following compounds would be a white, crystalline solid?
(A) ${C_2}{H_5}$
(B) $CO$
(C) $CuC{l_2}$
(D) $C{r_2}{O_3}$
(E) $MgO$

Answer 1

A crystalline solid is a solid material whose constituents are arranged in a highly ordered microscope structure, forming a crystal lattice which extends in all the directions. So here in this question, from the following compounds we have to find out the most crystalline solid.

Complete step by step answer:
So the solid we have fixed composition and three dimensional structure is called as crystalline solid. Firstly there are some points by which we identify a crystalline solid. The components can be arranged in a regular repeating three-dimensional array, which results in a crystalline solid, or more or less randomly to produce an amorphous solid. Moreover, crystalline solid have well-defined edges and faces diffract x-rays and tend to have sharp melting points.
So as from the above options, $MgO$ that is Magnesium Oxide would be white crystalline solid. Magnesium oxide is an ionic compound, formed by the transfer of electrons from one element to the other. Since it is an ionic compound. $MgO$ is solid. It is also a white and crystalline in nature. It is a white hygroscopic solid mineral as it occurs naturally as periclase and is a source of magnesium. Due to its stability. $MgO$ is used as a model system just for investigating vibrational properties of crystals.

So, the correct answer is Option E.

Additional information:
Point to be noted that magnesium fires cannot be extinguished by water. Magnesium continues to burn after oxygen is depleted. Further, it then reacts with nitrogen from air to form magnesium nitride($M{g_3}{N_2}$). As you are probably familiar with rust which is simply the oxide that forms when iron is exposed to oxygen in the air. With magnesium, the oxide layers form a white coating on the outside of the metal that will slow down or interfere with the burning process.

Note: Oxygen and magnesium come together in a chemical reaction to form this compound and after it burns, it forms a white powder of the magnesium oxide. Moreover, Magnesium gives up two electrons to oxygen atoms just to form this powdery product.