Answer : The mass of KNO₃ added must be,
Explanation : Given,
Molal-freezing-point-depression constant for water =
Volume of water = 275 mL
Molar mass of KNO₃ = 101.1 g/mole
First we have to calculate the mass of water.
Density of water = 1.00 g/mL
Now we have to calculate the mass of KNO₃
Formula used :
where,
= change in freezing point
= freezing point of solution =
= freezing point of water =
i = Van't Hoff factor = 2 (for KNO₃ electrolyte)
= freezing point constant for water =
m = molality
Now put all the given values in this formula, we get
Therefore, the mass of KNO₃ added must be,