Answer:
11.52g of ethanol
Explanation:
Molality is an unit of concentration defined as ratio between moles of solute (In this case, ethanol) and kg of solvent.
As solvent is water, 1 liter of water weights 1kg.
That means to create a 0.25molal solution it is necessary to have 0.25 moles of ethanol.
Molar weight of ethanol (C₂H₆O) is:
C: 12.01g/mol × 2 = 24.02g/mol
H: 1.01g/mol × 6 = 6.06g/mol
O: 16g/mol × 1 = 16g/mol
24.02g/mol + 6.06g/mol + 16g/mol = 46.08g/mol
As you need 0.25 moles, there is necessary to weight:
0.25 moles × (46.08g/mol) = <em>11.52g of ethanol</em>
