# How many neutrons in 5*mol of water?

Apr 28, 2017

Well, how many neutrons in A SINGLE ${H}_{2} O$ $\text{molecule}$..........?

#### Explanation:

To a first approximation we have a single molecule of ""^(1)H_2^(16)O. (The left hand superscripts, as always, refer to the nuclear mass, the isotope. Of course there are some different (so-called) isotopomers, but we really don't have to worry about them given their abundance.)

So for ""^16O there are $\text{8 neutrons}$, and for ""^1H there are NO neutrons. If you don't know how I knew this I would review your knowledge of isotopes.......

So we know the number of neutrons of in one molecule molecule, we just multiply this number out by the molar quantity:

$\text{Number of neutrons}$ $=$ $\text{8 neutrons} \times {N}_{A} \times 5$, where ${N}_{A} = \text{the Avocado Number........}$

And when you do this problem, can you calculate how neutrons in the same quantity of ${D}_{2} O$, where D=""^2H? ${D}_{2} O$ is often used in a laboratory.