Question

What is heavy water?
A. ${H_2}{O^{18}}$
B. ${D_2}O$
C. ${H_2}{O^{17}}$
D. ${H_2}O$

Answer 1

We must know that hydrogen is the lightest atom with only one electron in it. It has three isotopes, namely: protium (${}_1^1{\text{H}}$), deuterium (D or${}_1^2{\text{H}}$) and tritium (T or${}_1^3{\text{H}}$). Therefore, deuterium is heavier than protium by one neutron that is why water made from deuterium is called heavy water.

Complete answer:
We must know that in ordinary water (${{\text{H}}_{\text{2}}}{\text{O}}$), each hydrogen ${\text{,H}}$ atom has just a single proton in its nucleus. In heavy water, each hydrogen atom is heavier as it contains a neutron as well as a proton in its nucleus. This isotope of hydrogen is called deuterium. Heavy water's more scientific name is deuterium oxide, abbreviated as ${{\text{D}}_{\text{2}}}{\text{O}}$.

Therefore, the correct option is B.

Note:
Heavy water has a wide range of applications that is normally not afforded by ordinary water. Also, heavy water is heavier than normal water. The ice of heavy-water will sink in normal water.
Use of heavy water:
1. A heavy water reactor finds application as a coolant and moderator.
2. Deuterium works as a moderator as it has the ability to absorb fewer neutrons than hydrogen. This process is extremely important as nuclear fission reactions require neutrons to carry out their chain reactions. Therefore, it is extensively used as a moderator in nuclear reactors.
3. We can use heavy water in chemical laboratories in exchange reactions for the study of reaction mechanisms.
4. It could be synthesized by exhaustive electrolysis of water also as a by-product in some fertilizer industries.
5. It is also used for the preparation of other deuterium compounds, for example:
${\text{Ca}}{{\text{C}}_{\text{2}}}{\text{ + 2}}{{\text{D}}_{\text{2}}}{\text{O}} \to {\text{}}{{\text{C}}_{\text{2}}}{{\text{D}}_{\text{2}}}{\text{ + Ca}}{\left( {{\text{OD}}} \right)_{\text{2}}}$