What do particulates in the atmosphere do? A: They trap heat
B: They help plants to grow better
C: They shield Earth's surface from harmful solar radiation
D: They nucleate water vapor to form clouds.

Given mass of solute = 340 gram
Molar mass of solute(MgBr2) = 184 g

Number of moles = Given mass / Molar mass = 340 / 184 = 1.85 moles

Now, Molarity = Number of moles / solution (in litres)

So, M = 1.85 / 8
M = 0.23 M

In short, Your Molarity would be: 0.23 M

Hope this helps!