Need help on an school exercise pleeease (Oceanograpy)?

Question

Question:

1- If you add 4.8g of salt to fresh water to make a liter of sea water what is the resulting salinity in %o(parts per thousand)?

Answer 1

What you need here is the density of salt water to find the answer.  The density of salt water is 1.025g/cm3.  Since density - Mass/volume you divide the mass (4.8 grams) by the density 1.025g/cm3.  This gives you the volume which is 4.68cm3.  Centimeters cubed is the same as a milliliter so you have 4.68 mL.  You then divide 4.68mL by 1000mL (liters) to get 0.00468.  Multiply it by a hundred and you get 0.468ppt.  

Hope this helps