What is the boiling point of a solution that contains 3 moles of #KBr# in 2000 g of water? (#K_b# = 0.512 C/m; molar mass of water = 18 g)?

1 Answer
Junaid Mirza
Apr 20, 2018

#"101.536 °C"#

Explanation:

When a solute is added in a solvent the boiling of solvent is elevated.

This elevation in boiling point (#Delta"T"_b#) is given by the formula

#Δ"T" = i"K"_b"m"#

Where

  • #i =# Van’t Hoff factor (#2# for #"KBr"#)
  • #"K"_b =# Boiling point constant (#"0.512 °C/molal"# for water)
  • #"m ="# Molality of solution#= "Moles of solute"/"Mass of solvent (in kg)"#

Here solute is glucose & solvent is water.
Boiling point of pure water is #"100°C"#

#("T" - "100°C") = cancel"2" × "0.512°C/molal" × "3.00 mol"/(cancel"2.00" "kg")#

#"T = 100°C + 1.536°C = 101.536°C"#

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