Answer:
KBr final solution:
V = 250mL --> 0.25L
Concentration/Molarity = 1.5 mol/L
To find the amount of moles of KBr here, just multiply the volume by the concentration (0.25 x 1.5 = 0.375 mol)
So the amount of moles for KBr is 0.375 mol. Now we know that the mass divided by the molar mass (the atomic mass values of K and Br in the periodic table added together) would give us the amount of moles aswell.
n = moles
m = mass
M = molar mass
n = m/M
so if we rearrange this equation to find mass, we would get:
m = n x M
Molar mass for KBr: (39.09) of K + (79.90) of Br = 118.99
m = 0.375 mol x 118.99
m = 44.62g
Therefore 44.62g of KBr is needed to make 250mL of a 1.5 M KBr solution.