Question

0.040mol of (NH4)2Ni(SO4)2•6H2O is dissolved in water to give 200cm3 of aqueous solution. What is the concentration, in mol dm–3, of ammonium ions?

Answer 1

`"Concentration"="Moles of solute"/"Volume of solution"......=0.40*mol*dm^-3.`

Explanation:

`"Concentration with respect to the nickel salt"`

`=(0.040*mol)/(0.200*dm^3)=0.20*mol*dm^-3`

But given the formulation of the salt, #(NH_4)_2[Ni (SO_4)_2]*6H_2O#, there are 2 equiv of ammonium per equiv of salt. And thus `[NH_4^+]=0.40*mol*dm^-3`