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The boiling point of heavy water is?
A. $100{}^\circ C$
B. $101.4{}^\circ C$
C. $99{}^\circ C$
D. $110{}^\circ C$

Last updated date: 29th Feb 2024
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IVSAT 2024
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Hint: Think about the chemical formula of heavy water and how it will affect the physical and chemical properties of water with respect to regular water.

Complete step by step answer:
 The term heavy water implies that due to some change in the chemical formula of regular water, its molecular mass is greater. This change is caused due to the substitution of hydrogen in regular water by deuterium, which is the heavier isotope of hydrogen with a molecular mass of 2 instead of 1. So, the chemical formula of heavy water is written as ${{D}_{2}}O$. This deuterium has 1 neutron and 1 proton in its nucleus. Another isotope of hydrogen called Tritium $(T)$ has 2 neutrons and 1 proton in its nucleus, so its atomic mass is 3. But since this ${{T}_{2}}O$ is highly radioactive and corrosive it is usually removed.
The bonds that are formed by this deuterium $(D)$ with oxygen are found to be stronger than the ones formed by hydrogen $(H)$. Thus, it takes more energy to excite these intermolecular, hydrogen bonds and cause their breakage. The boiling and melting point of heavy water is found to be slightly more than that of heavy water.
Hence, the answer is ‘B. $101.4{}^\circ C$’

Hence, the correct answer is option B.

Do not assume that since just a neutron is added, none of the physical properties should change and only chemical properties will change and mark the answer as ‘A. $100{}^\circ C$’. Remember that the mass of the nucleus is doubling and it is bound to cause some changes in the physical properties of the compounds formed by it.
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