Which of the following statements about boiling points are true?
A. The boiling point of 0.1 m NaF(aq) is lower than the boiling point of 0.1 m methanol(aq).
B. The boiling point of a 0.5 m aqueous solution of LiOH is the same as the boiling point of a 0.5 m aqueous solution of LiCl.
C. The boiling point of a solution made by dissolving 10 g of C2H6O2 in 0.30 kg of water is higher than the boiling point of a solution of 10 g of NaCl in 0.30 kg of water.
D. The boiling point of 2 m KF in water is 102.4ºC.
E. The boiling point of 1 m aqueous KNO3 is higher than the boiling point of 1 m aqueous Ba(NO3)2.
All of these can be answered with delta T = i*Kf*m or i*Kb*m
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A 10 g mixture of glucose and urea present in 250 ml solution show that osmotic pressure of 7.4 atm at 27°c .calculate % composition of mixture
To determine which of the statements about boiling points are true, we can consider the concept of boiling point elevation and the colligative properties of solutes dissolved in a solvent.
Boiling point elevation refers to the phenomenon where the boiling point of a solvent increases when a solute is dissolved in it. This is because the presence of solute particles disrupts the intermolecular forces between the solvent molecules, making it harder for them to escape into the vapor phase.
The degree of boiling point elevation depends on the concentration of the solute in the solution. The higher the concentration, the greater the boiling point elevation.
Based on this information, let's evaluate each statement:
A. The boiling point of 0.1 m NaF(aq) is lower than the boiling point of 0.1 m methanol(aq).
To determine this, we need to compare the effect of NaF and methanol as solutes on the boiling point of water. Since NaF is an ionic compound, it dissociates into Na+ and F- ions when dissolved in water. These ions will increase the boiling point of water more significantly compared to methanol, which is a molecular compound. Therefore, Statement A is false, as the boiling point of 0.1 m NaF(aq) is higher than the boiling point of 0.1 m methanol(aq).
B. The boiling point of a 0.5 m aqueous solution of LiOH is the same as the boiling point of a 0.5 m aqueous solution of LiCl.
Both LiOH and LiCl are ionic compounds and fully dissociate into ions in water. As a result, they have a similar effect on the boiling point of water. Therefore, Statement B is true, as the boiling point of a 0.5 m aqueous solution of LiOH is the same as the boiling point of a 0.5 m aqueous solution of LiCl.
C. The boiling point of a solution made by dissolving 10 g of C2H6O2 in 0.30 kg of water is higher than the boiling point of a solution of 10 g of NaCl in 0.30 kg of water.
The boiling point elevation depends on the concentration of the solute, not the mass. So, in this case, if both solutes have the same concentration, they will have a similar effect on the boiling point of water. Therefore, Statement C is false, as the boiling point will be the same for both solutions.
D. The boiling point of 2 m KF in water is 102.4ºC.
To determine this, we need to examine the effect of KF as a solute on the boiling point of water. The concentration of 2 m indicates that there are two moles of KF dissolved in one liter of water. KF is an ionic compound and fully dissociates into K+ and F- ions. The presence of these ions leads to a significant increase in the boiling point of water. Therefore, Statement D is true, as the boiling point of 2 m KF in water is indeed higher than 100ºC.
E. The boiling point of 1 m aqueous KNO3 is higher than the boiling point of 1 m aqueous Ba(NO3)2.
Both KNO3 and Ba(NO3)2 are ionic compounds and fully dissociate into ions in water. However, Ba2+ is a larger cation compared to K+, and this size difference leads to a stronger ion-dipole interaction between Ba2+ and water molecules. As a result, Ba(NO3)2 will have a greater effect on the boiling point of water compared to KNO3. Therefore, Statement E is false, as the boiling point of 1 m aqueous KNO3 is lower than the boiling point of 1 m aqueous Ba(NO3)2.
In summary:
Statement A is false.
Statement B is true.
Statement C is false.
Statement D is true.
Statement E is false.