How much salt (in grams) must be added to a two liter bottle of pure water to make the resulting mixture 0.035 percent salt by weight

0.7g of salt.

Explanation:

% concentration by mass =

mass of solute/mass of solution

Solute is the salt

Solution is salt +water

Mass of water = Density of water × volume of water

Mass of water = 1000g/L × 2L

Mass of water = 2000g

Let mass of salt = x

Mass of solution = x+2000

0.035/100 = x/x+2000

0.035(x+2000) = 100x

70= 99.965x

x= 0.7g

Therefore the mass of salt to be added is 0.7g