[tex]\text{Molar mass of KBr},~ M = 119.002~ \text{g mol}^{-1}[/tex]
[tex]\text{No. of moles,}~ n = 3~ \text{mol.}\\\\\text{Mass of KBr},~ w = nM = 3 \times 119.002= 357.006~ g\\\\\text{Hence, there are 357.006 grams in 3 moles of KBr.}[/tex]