Q13.85 - Chemistry: Molecular Nature Of Matter And Change

Question

Question: Which aqueous solution has a boiling point closer to its predicted value, 0.050 m  NaF or 0.50 m ? Explain.

 

Step-by-Step Solution

Answer

Answer

 

0.050m NaF solution has a boiling point closer to its predicted value than 0.50m KCI because former is more dilute and van’t Hoff factors (i) approach their ideal values as the solution becomes more dilute

Step 1: van’t Hoff factor

 

The van't Hoff factor is the difference between the concentration of a material determined by its mass and the concentration of particles actually formed when the substance is dissolved.

Step 2: Effect of concentration

 

Here both NaF and KCI have same value of (i), so relative elevation in boiling point will be same in both the solutions but as gases display nearly ideal behavior at low pressures because the distances between particles are large. An electrolyte solution that has been diluted will behave better than one that has been concentrated.

 

Similarly, van’t Hoff factors (i) approach their ideal values as the solution becomes more dilute, because the distance between ions increases.

 

Thus, 0.050 m NaF  has a boiling point closer to its predicted value.