What is the molar mass of heavy water #"D"_2"O"#?

1 Answer
Aug 17, 2016

Answer:

#"20.0276 g mol"^(-1)#

Explanation:

Heavy water, #"D"_2"O"#, is what you get when you replace the hydrogen-1 isotopes, #""^1"H"#, that are usually present in the vast majority of water molecules, with deuterium, or hydrogen-2 isotopes, #""^2"H"#.

The difference between hydrogen-1 and deuterium is that the latter contains one proton and one neutron inside its nucleus, as opposed to the former which only contains a proton.

http://www.ces.fau.edu/nasa/module-3/how-is-temperature-measured/isotopes.php

Now, deuterium has a molar mass of

#M_("M D") = "2.0141 g mol"^(-1)#

https://en.wikipedia.org/wiki/Deuterium

This means that the molar mass of heavy water, which contains two deuterium isotopes and one oxygen atom, will be equal to

#M_("M D"_2"O") = 2 xx "2.0141 g mol"^(-1) + "15.9994 g mol"^(-)#

#color(green)(|bar(ul(color(white)(a/a)color(black)(M_("M D"_2"O") = "20.0276 g mol"^(-1))color(white)(a/a)|)))#