How many grams in 3.75 mol of #NaBr#?
You can find how many grams would be equivalent to
As you know, the mass of one mole of a compound is expressed by that compound's molar mass. Sodium bromide has a molar mass
You can thus use the molar mass of a compound to convert between its mass and the number of moles equivalent to that mass. In your case, you will have
#3.75 color(red)(cancel(color(black)("moles NaBr"))) * overbrace("102.9 g"/(1color(red)(cancel(color(black)("mole NaBr")))))^(color(purple)("molar mass")) = "385.875 g"#
You need to round this off to three sig figs, the number of sig figs you have for the number of moles of sodium bromide
#m_(NaBr) = color(green)("386 g")#