There are mol of bromide ions in 0.700 L of a 0.400 M solution of AlBr

The number of moles of AlBr3 = Molarity × Volume

= 0.400 × 0.700

= 0.28 moles

1 mole of AlBr3 gives 3 moles of Br- ions

That is

AlBr3 = Al3+ + 3Br-

Therefore, 0.045 moles of AlBr3 will yield 3 × 0.28 = 0.84 moles

Thus; they are 0.84 moles of bromide ions

h let me think