1. Understand the Formula:

* MgBr₂ is magnesium bromide. It dissociates in solution to form one Mg²⁺ ion and two Br⁻ ions:

MgBr₂(aq) → Mg²⁺(aq) + 2Br⁻(aq)

2. Calculate Moles of MgBr₂:

* We're given the volume (750.0 mL) and molarity (1.35 M) of the MgBr₂ solution.

* Convert the volume to liters: 750.0 mL * (1 L / 1000 mL) = 0.750 L

* Use the molarity formula to find moles:

Moles = Molarity * Volume

Moles = 1.35 mol/L * 0.750 L = 1.0125 mol MgBr₂

3. Calculate Moles of Bromide Ions:

* From the balanced equation, we see that 1 mole of MgBr₂ produces 2 moles of Br⁻ ions.

* Therefore, moles of Br⁻ = 1.0125 mol MgBr₂ * (2 mol Br⁻ / 1 mol MgBr₂) = 2.025 mol Br⁻

Answer: There are 2.025 moles of bromide ions present in 750.0 mL of 1.35 M MgBr₂ solution.