The answer is 296.3g296.3g.
Saline solution is a mixture of table salt (NaClNaCl) and water (H_2OH2O).
The solution's percent concentration by mass, defined as the mass of solute (in this case, NaClNaCl) divided by the total mass of the solution and multiplied by 100%, is said to be 1.25%1.25%.
The total mass of the solution is equal to
m_(solut ion) = m_(NaCl) + m_(water)msolution=mNaCl+mwater
Knowing that c% = m_(solute)/(m_(solut ion)) * 100%c%=msolutemsolution⋅100%, and that the
mass of the solution is 300g300g, we can determine the mass of NaClNaCl by
m_(NaCl) = (c * m_(solut ion))/100 = (1.25 * 300)/100 = 3.75gramsmNaCl=c⋅msolution100=1.25⋅300100=3.75grams
This means that the mass of water is equal to
m_(water) = m_(solut ion) -m_(NaCl) = 300- 3.75 = 296.3 gramsmwater=msolution−mNaCl=300−3.75=296.3grams, 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%1.25%.