Table of contents

1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 38m
5. BONUS: Mathematical Operations and Functions48m
6. Chemical Quantities & Aqueous Reactions3h 53m
7. Gases3h 49m
8. Thermochemistry2h 37m
9. Quantum Mechanics2h 58m
10. Periodic Properties of the Elements3h 9m
11. Bonding & Molecular Structure3h 29m
12. Molecular Shapes & Valence Bond Theory1h 57m
13. Liquids, Solids & Intermolecular Forces2h 23m
14. Solutions3h 1m
15. Chemical Kinetics2h 53m
16. Chemical Equilibrium2h 29m
17. Acid and Base Equilibrium5h 1m
18. Aqueous Equilibrium4h 47m
19. Chemical Thermodynamics1h 50m
20. Electrochemistry2h 42m
21. Nuclear Chemistry2h 36m
22. Organic Chemistry5h 7m
23. Chemistry of the Nonmetals2h 39m
24. Transition Metals and Coordination Compounds3h 16m

14. Solutions

Freezing Point Depression

General Chemistry

14. Solutions

Freezing Point Depression

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Multiple Choice

Calculate the freezing point of an aqueous solution with 95.21 g of barium chloride (BaCl2) dissolved in 1750 mL of water. Assume complete dissociation and use the freezing point depression constant (Kf) for water as 1.86 °C/m.

-0.93 °C

-5.58 °C

-1.86 °C

-3.72 °C

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Verified step by step guidance

First, calculate the molar mass of barium chloride (BaCl2). The molar mass is the sum of the atomic masses of barium (Ba) and two chlorine (Cl) atoms. Use the periodic table to find these values: Ba = 137.33 g/mol, Cl = 35.45 g/mol. Therefore, the molar mass of BaCl2 is 137.33 + 2(35.45) g/mol.

Next, determine the number of moles of BaCl2 in the solution. Use the formula: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \). Substitute the given mass of BaCl2 (95.21 g) and the calculated molar mass from the previous step.

Calculate the molality of the solution. Molality (m) is defined as the number of moles of solute per kilogram of solvent. First, convert the volume of water (1750 mL) to mass, assuming the density of water is 1 g/mL, so 1750 mL of water is 1750 g or 1.75 kg. Then, use the formula: \( m = \frac{\text{moles of solute}}{\text{mass of solvent in kg}} \).

Determine the van't Hoff factor (i) for BaCl2. Since BaCl2 dissociates completely into three ions (Ba\(^{2+}\) and 2 Cl\(^{-}\)), the van't Hoff factor is 3.

Finally, calculate the freezing point depression using the formula: \( \Delta T_f = i \cdot K_f \cdot m \). Substitute the values for the van't Hoff factor (i = 3), the freezing point depression constant (Kf = 1.86 °C/m), and the molality calculated in the previous step. The result will give you the change in freezing point, which you subtract from the normal freezing point of water (0 °C) to find the new freezing point.