Select the correct answer.

Which of these solutes raises the boiling point of water the most?

A. molecular sucrose [tex]$\left( C_{12}H_{22}O_{11} \right)$[/tex]
B. ionic sodium chloride [tex]$( NaCl )$[/tex]
C. ionic potassium bromide [tex]$( KBr )$[/tex]
D. ionic calcium chloride [tex]$\left( CaCl_2 \right)$[/tex]
E. ionic aluminum fluoride [tex]$\left( AlF_3 \right)$[/tex]



Answer :

To determine which solute raises the boiling point of water the most, we need to understand the concept of boiling point elevation, which is a colligative property. This means that the boiling point elevation depends on the number of particles in solution rather than the specific type of particles.

Here’s a step-by-step analysis:

1. Molecular Sucrose [tex]$\left(C_{12}H_{22}O_{11}\right)$[/tex]:
- Sucrose is a molecular compound and does not dissociate in water.
- It remains as a single molecule: \(C_{12}H_{22}O_{11} \rightarrow C_{12}H_{22}O_{11}\).
- Number of particles in solution: 1 molecule.

2. Ionic Sodium Chloride [tex]$(NaCl)$[/tex]:
- Sodium chloride is an ionic compound and dissociates completely in water.
- \(NaCl \rightarrow Na^+ + Cl^-\).
- Number of particles in solution: 2 ions (one \(Na^+\) and one \(Cl^-\)).

3. Ionic Potassium Bromide [tex]$(KBr)$[/tex]:
- Potassium bromide is an ionic compound and dissociates completely in water.
- \(KBr \rightarrow K^+ + Br^-\).
- Number of particles in solution: 2 ions (one \(K^+\) and one \(Br^-\)).

4. Ionic Calcium Chloride [tex]$\left(CaCl_2\right)$[/tex]:
- Calcium chloride is an ionic compound and dissociates completely in water.
- \(CaCl_2 \rightarrow Ca^{2+} + 2Cl^-\).
- Number of particles in solution: 3 ions (one \(Ca^{2+}\) and two \(Cl^-\)).

5. Ionic Aluminum Fluoride [tex]$\left(AlF_3\right)$[/tex]:
- Aluminum fluoride is an ionic compound and dissociates completely in water.
- \(AlF_3 \rightarrow Al^{3+} + 3F^-\).
- Number of particles in solution: 4 ions (one \(Al^{3+}\) and three \(F^-\)).

Boiling point elevation is proportional to the number of particles in the solution. More particles mean a greater elevation in the boiling point.

- Sucrose: 1 particle
- Sodium Chloride: 2 particles
- Potassium Bromide: 2 particles
- Calcium Chloride: 3 particles
- Aluminum Fluoride: 4 particles

As we can see, aluminum fluoride [tex]$\left(AlF_3\right)$[/tex] produces the highest number of particles, 4 ions per formula unit.

Thus, ionic aluminum fluoride [tex]$\left(AlF_3\right)$[/tex] raises the boiling point of water the most.

The correct answer is:
[tex]\[ \text{E. ionic aluminum fluoride } (AlF_3) \][/tex]

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