What is the expected boiling-point elevation of water for a solution that contains 216 g of sodium chloride dissolved in 1.0 kg of water?

Answer in units of degrees Celsius.

1 Answer
Al E.
Jan 13, 2018

Boiling point elevation is a colligative property of solutions. To be sure, its magnitude is directly proportional to the concentration of solute in the solution. Consider,

#DeltaT_b = iK_bm#

Hence,

#DeltaT_b = 2.0 * (0.512°C)/m * (216g * ("mol")/(58.5g))/(1.0kg)#
#therefore DeltaT_b approx 3.78°C#

For the purposes of this problem which appears to be relatively trivial, I didn't account for ion-pairing in solution. If the question expressly said to account for this, we would say #i = 1.9#. To be sure, sodium chloride wouldn't "cleanly" dissociate as it did here, rather periodically bonding and breaking again.

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