Question

What is the molar concentration of ammonia in a `35%` `w/w` solution for which `rho_"solution"=0.88*g*mL^-1`?

Answer 1

We can address the number of ammonia molecules in conc. ammonia.........

Explanation:

Concentrated ammonia is an aqueous solution of ammonia in water. Pure ammonia is a room temperature gas.

At room temperature, the density of a saturated solution in water is `rho=0.88*g*mL^-1`, and has a concentration of `35%w/w`...

And we can thus work out its concentration in `mol*L^-1`....

`((0.88*g*mL^-1xx35%)/(17.03*g*mol^-1))/(1xx10^-3*L*mL^-1)=18.1*mol*L^-1`

And thus in `10*L` conc. ammoniacal solution, there are `180.1*mol` ammonia, i.e. ....

`180.1*molxx6.022xx10^23*"ammonia molecules"*mol^-1=`

`"A lot of ammonia molecules."`

Of course in this solution there are still a lot more water molecules, each of which contributes one oxygen atom, and 2 hydrogen atoms.