No se :/, a ti si te paso??
Answer:
5.85 grams of NaCl should be added to 250 grams of water to make a 0.40 m solution.
Explanation:

Mass of NaCl =x
Molar mass of NaCl = 58.5 g/mol
Molality of the solution = 0.40 m
Mass of the solvent = 250 g = 0.250 kg (1g = 0.001 kg)


5.85 grams of NaCl should be added to 250 grams of water to make a 0.40 m solution.
Ok well whats the questions
If we remove 2 electrons, the new charge will be positive by 2 units. Hence, the ion is

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It depends on other factors to. techniqually this doesent take place in time so it could be that in the future that will be enough but you are probably right. most appliances could not heat water with .1 lb of propane. though it would be luke warm