Ch.12 - SolutionsWorksheetSee all chapters
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Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: How many moles of CO(NH 2)2 are present in 131 g of water, if the freezing point of the solution is −4.02 °C? kf (water) =1.86 C • kg/mol.1. 0.263 mol2. None of these3. 0.280 mol4. 0.297 mol5. 0.288 m


How many moles of CO(NH 2)2 are present in 131 g of water, if the freezing point of the solution is −4.02 °C? kf (water) =1.86 C • kg/mol.

1. 0.263 mol

2. None of these

3. 0.280 mol

4. 0.297 mol

5. 0.288 mol

6. 0.272 mol


We’re being asked to determine the moles of CO(NH2)2 present in 131 g water to get a solution with a freezing point of –4.02 ˚C.

Recall that the freezing point of a solution is lower than that of the pure solvent and the change in freezing point (ΔT­f) is given by:

ΔTf=Tf, pure solvent-Tf, solution

The change in freezing point is also related to the molality of the solution:



i = van’t Hoff factor

m = molality of the solution (in m or mol/kg)

Kf = freezing point depression constant (in ˚C/m)

Recall that the molality of a solution is given by:

molality=moles solutekg solvent

For this problem, we need to do the following:

Step 1: Calculate for ΔTf.

Step 2: Determine the molality of the solution.

Step 3: Calculate the mass of CO(NH2)2 present.

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