mass of solvent, kg ) 4. Determine the value for the van't Hoff factor (i) for each of your solutes. For molecular solutes the value is i = 1. For ionic solutes, you can determine the value of i by examining the molecular formula. The value will be a small whole number; partial ionization is not expected, and waters of hydration are not included.

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Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
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Chapter1: Chemical Foundations
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Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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I need help with question 4. 

 

The initial temperature for all 3 is 0.9 degrees C. 

Calculations
1. Using the solute formulas provided, convert grams of solute to moles of solute. For the hydrated
salts be sure to include the waters of hydration in the molar mass.
2. It is reasonable to assume that the total mass of solvent includes the mass of both the water
and the ice. If you used exactly 50.0 g of each, then you would have used 100.0 g or 0.100 kg of
solvent. Use the actual masses of water and ice recorded in your lab notebook to calculate the
mass of solvent.
3. Calculate the molality of the solution using the moles of solute (from Step 1) and the mass of
solvent (from Step 2):
moles of solute
mass of solvent, kg
molality, m =
4. Determine the value for the van't Hoff factor (i) for each of your solutes. For molecular solutes
the value is i = 1. For ionic solutes, you can determine the value of i by examining the molecular
formula. The value will be a small whole number; partial ionization is not expected, and waters
of hydration are not included.
5. Calculate the theoretical freezing point depression for each of the solutions in °C. The k, for
water is 1.86°C/m.
6. Calculate the theoretical freezing point of each solution, and compare it with the
experimentally observed freezing point for your solutes.
7. Comment in your lab notebook about the relationship between the observed freezing points
and the number of particles in solution (i) for each solute.
14
Colligative Pr o perties of Solutions- Freezing Point Depression | Labor atory 2
Transcribed Image Text:Calculations 1. Using the solute formulas provided, convert grams of solute to moles of solute. For the hydrated salts be sure to include the waters of hydration in the molar mass. 2. It is reasonable to assume that the total mass of solvent includes the mass of both the water and the ice. If you used exactly 50.0 g of each, then you would have used 100.0 g or 0.100 kg of solvent. Use the actual masses of water and ice recorded in your lab notebook to calculate the mass of solvent. 3. Calculate the molality of the solution using the moles of solute (from Step 1) and the mass of solvent (from Step 2): moles of solute mass of solvent, kg molality, m = 4. Determine the value for the van't Hoff factor (i) for each of your solutes. For molecular solutes the value is i = 1. For ionic solutes, you can determine the value of i by examining the molecular formula. The value will be a small whole number; partial ionization is not expected, and waters of hydration are not included. 5. Calculate the theoretical freezing point depression for each of the solutions in °C. The k, for water is 1.86°C/m. 6. Calculate the theoretical freezing point of each solution, and compare it with the experimentally observed freezing point for your solutes. 7. Comment in your lab notebook about the relationship between the observed freezing points and the number of particles in solution (i) for each solute. 14 Colligative Pr o perties of Solutions- Freezing Point Depression | Labor atory 2
Molality
i
Theoretical
Mass of
Mass of
Mass of
Observed
Solute
solute (g)
ice (g)
water (g)
f.p. (°C)
(m)
f.p. (°C)
2.91 4894 49.92-1°C 049
NaCl
CaCl, · 2H;O 7.37 5643 51.700.0c 013
17.12 A85 51.17
NA
C12H2„O11
0.క 043
5°C
Fe(NO3)3 · 9H2O|NA
NA
NA
NA NA NA
Transcribed Image Text:Molality i Theoretical Mass of Mass of Mass of Observed Solute solute (g) ice (g) water (g) f.p. (°C) (m) f.p. (°C) 2.91 4894 49.92-1°C 049 NaCl CaCl, · 2H;O 7.37 5643 51.700.0c 013 17.12 A85 51.17 NA C12H2„O11 0.క 043 5°C Fe(NO3)3 · 9H2O|NA NA NA NA NA NA
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