The answer is 4.9 moles. Solution: Using the equation for boiling point elevation Δt, Δt = i Kb m we can rearrange the expression to solve for the molality m of the solution: m = Δt / i Kb
Since we know that pure water boils at 100 °C, and the Ebullioscopic constant Kb for water is 0.512 °C·kg/mol, m = (105°C - 100°C) / (2 * 0.512 °C·kg/mol) = 4.883 mol/kg
From the molality m of the solution of salt added in a kilogram of water, we can now find the number of moles of salt: m = number of moles / 1.0kg number of moles = m*1.0kg = (4.883 mol/kg) * (1.0kg) = 4.9 moles
If you apply a force over a given distance - you have done work. Work = Change in Energy. If an object's kinetic energy or gravitational potential energy changes, then work is done. The force can act in the same direction of motion.
