The answer is #296.3g#.
Saline solution is a mixture of table salt (#NaCl#) and water (#H_2O#).
The solution's percent concentration by mass, defined as the mass of solute (in this case, #NaCl#) divided by the total mass of the solution and multiplied by 100%, is said to be #1.25%#.
The total mass of the solution is equal to
#m_(solut ion) = m_(NaCl) + m_(water)#
Knowing that #c% = m_(solute)/(m_(solut ion)) * 100%#, and that the
mass of the solution is #300g#, we can determine the mass of #NaCl# by
#m_(NaCl) = (c * m_(solut ion))/100 = (1.25 * 300)/100 = 3.75grams#
This means that the mass of water is equal to
#m_(water) = m_(solut ion) -m_(NaCl) = 300- 3.75 = 296.3 grams#, which makes sense since the bulk of this particular solution must be represented by water, given the fact that its percent concentration by mass is #1.25%#.
