The difference between the wattage is 60-18=42W. The saving in energy over 10 hrs is 10×42=420 watt-hours=0.42kWh
We will get the molality from this formula:
Molality = no.of moles of solute / Kg of solvent
So first we need the no.of moles of KNO3 = the mass of KNO3 / molar mass of KNO3
no.of moles of KNO3 = 175 / 101.01 = 1.73 mol
By substitution in the molality formula:
∴ molality = 1.73 / (750/1000) = 2.3 Molal
B) 50 J because it had less energy at the beginning than the end
