Prelab for Kf Lab SD Flashcards

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general chemistry ii lab
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1

What is the van't Hoff factor (i) for sodium chloride?

  • 1
  • 2
  • 3
  • 4

2

2

About how much sodium chloride will be used in a single trial of this experiment?

  • 1-2 g
  • 2-5 g
  • 5-8 g
  • 8-11 g

2-5 g

3

A salt water solution is found to have a mass of 117.25 grams. If 5.40 grams of sodium chloride was originally added, how many grams of water are in the solution?

117.25 g salt water solution - 5.40 g sodium chloride = 111.85 g water

4

A solution of contains 118.7 g of water and 7.778 grams of sodium chloride. What is its molality in mol/kg? HINT: Molality = moles of solute/kg of solvent.

7.778 g NaCl x ( 1 mol NaCl / 58.44 g NaCl ) = 0.1331 mol NaCl

118.7 g H2O x ( 1 kg / 1000 g) = 0.1187 kg H2O

molality (m) = mol of solute / kg of solvent

m = 0.1331 mol NaCl / 0.1187 kg H2O = 1.1213 mol/kg

Ex.

https://socratic.org/questions/how-do-you-calculate-molality-of-a-solution

https://www.youtube.com/watch?v=4rhfHkMT6mE

5

A (non-aqueous) solution is found to have a molality of 1.86 molal and experiences a freezing point depression of 7.90 degrees C. What is the Kf of the solvent (in degrees C/m)? HINT: Non-aqueous solutions do not tend to split into ions.

Kf = degrees C / m

Kf = 7.90 degrees C / 1.86 m

Kf = 4.25 degrees C/m