Question

How many moles of solute are present in (1.890x10^1) g of a (4.5x10^0) % w/w solution of sodium bromide? (answer to 2 s.d in mol)

Answer 1

4.5% means 4.5 g solute in 100 g solution. So in 18.90 g, there will be

4.5 g x (18.90/100) =? g NaBr.
Then mols NaBr = grams NaBr/molar mass NaBr = ?
Post your work if you get stuck.