The boiling point elevation is a colligative property, which depends on the number of solute particles in the solution:
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Since strong electrolytes like KNO3 and NaCl produce more particles in solution compared to weak electrolytes like CH3COOH and non-electrolytes like sucrose, the order of boiling points is: 1 N KNO3 = 1 N NaCl>1 N CH3COOH>1 N sucrose.