Seawater contains approximately 3.5%NaCl by mass and has a density of 1.02 g/mL.

Question

What volume of seawater contains 9.0 g of sodium?

Answer 1

mass of seawater= 9/.034=265grams
volume seawater=mass/density=265/1.02 ml

Answer 2

% Na in NaCl ... molar mass Na / molar mass NaCl

mass seawater needed ... (9.0 g / .035 NaCl/g) * %Na in NaCl

volume of seawater ... mass of seawater / density