Answer : The mole fraction of the total ions in an aqueous solution is 0.0248
Explanation :
First we have to calculate the moles of water.

Now we have to calculate the moles of magnesium ion and bromide ion.
As we are given that 0.4 moles of
that means, there are 0.4 moles of magnesium ion and 0.8 moles of bromide ions.
Total mole of ions in an aqueous solution = 0.4 + 0.8 = 1.2 mole
Now we have to calculate the mole fraction of the total ions in an aqueous solution.


Therefore, the mole fraction of the total ions in an aqueous solution is 0.0248