Now the molar mass of potassium bromide is #119.0*g*mol^-1#. How do I know this? Well, I have access to a Periodic Table that tells me the individual molar masses of atomic potassium, and atomic bromine. And by the way, you should have access to a Periodic Table as well. You will certainly be provided with a Periodic Table in every test of chemistry and fyzics you ever sit.
And so for the mass of #34.5*mol# quantity of this salt...we take the product...
#34.5*molxx119.0*g*mol^-1=??*g#...a tad over #4*kg#?