Question

What is the relation between molar mass of solute and boiling point elevation of solution?

• A. M₂ = \(\frac {1000\ △T_bW_2}{K_bW_1}\)
• B. M₂ = \(\frac {1000\ K_bW_2}{△T_bW_1}\)
• C. M₂ = \(\frac {△T_bW_1}{1000\ K_bW_2}\)
• D. M₂ = \(\frac {1000\ K_bW_1}{△T_bW_2}\)

Answer 1

The Correct Option is B

The relation between the molar mass of the solute (M₂) and the boiling point elevation of the solution (△T_b) can be given by the equation: 
△T_b = \(\frac {K_b . M_2 . W_2}{W_1}\)
where: 
△T_b is the boiling point elevation of the solution, 
K_b is the molal boiling point elevation constant, 
M₂ is the molar mass of the solute, 
W₂ is the weight (mass) of the solute, 
and W₁ is the weight (mass) of the solvent. 
To convert the equation into a more convenient form, we can multiply both sides by 1000: 
1000 . △T_b = \(\frac {1000 .K_b . M_2  .W_2}{W_1}\)
Simplifying, we have: 
M₂ = \(\frac {1000 . K_b . W_2}{△T_b . W_1}\) 
We can see that the correct relation is option (B): M₂ = \(\frac {1000 . K_b . W_2}{△T_b . W_1}\)