Ocean water contains 3.5 % NaCl by mass. What mass of ocean water in grams contains 46.8 g of NaCl?

1.3 kg

Explanation:

Mass of ocean water = mass of NaCl * (mass of ocean water/mass NaCl).

The % NaCl tells us there are 3.5 g NaCl/100 g ocean water or 100 g ocean water/3.5 g NaCl.

Mass of ocean water = 46.8 * (100/3.5)

Mass of ocean water = 46.8 * 28.6

Mass of ocean water = 1300 g = 1.3 kg

Note: The answer can have only two significant figures because that is all you gave for the percentage of NaCl.