Lab 7 – Molality Colligative Properties

Lab 7 – Molality Colligative Properties

Name: [First and Last]

Date: DD/MM/YYY

Experiment #: 7

Title:  Molality Colligative Properties

Purpose:

This experiment aims to explore the concept of molality and colligative properties. By calculating the molality of two salts and investigating their ability to lower the temperature of ice, students will learn about the relationship between solute concentration and freezing point depression. Students will also be able to observe the impacts of the salts on the melting point of ice cream during the preparation of ice cream. Our assignment help will hone your writing prowess for papers that will awe your professors.

Procedure: 

• Measure the mass of two pieces of ice from solutes NaCl and CaCl₂ and put them in two separate bags.
• Measure 0.5 moles of solutes NaCl and CaCl₂ and put them in different tubes.
• Pour 0.5 of moles (NaCl) and CaCl₂ into bags containing solute ice and mix
• Add a small bag containing milk into the bags containing ice together with 0.5 moles of solutes and mix.
• Record the initial temperature of each bag by dipping the thermometer probe into the bags.
• Shake the bags for further mixing
• Wait for 15 minutes and measure the temperatures again
• Separate the ice from the solute and milk and note the changes

Data/Results/Calculations:

1NaCl     → 1Na⁺   +   1Cl

1 mole of NaCl solids produces 1mole Na⁺ 1 mole Cl ^–   ions

Therefore, in all 2moles of ions Na⁺ + Cl ^–   yielded

1. Calcium Chloride: ion production

1 CaCl₂ → 1Ca²⁺ + 2Cl^–

1 mole of CaCl₂   produces 1 mole of Ca²⁺   2 moles of Cl ^–   ions

Therefore, in all 3 moles of ions   Ca²⁺ + Cl ^–    are produced

1. Molarity of Sodium Chloride

24g NaCl X1 mol NaCl/58g X 2moles/1moleNaCl = 1.0 mol NaCl ions

0.5mol NaCl  →   0.50mol Na⁺   + 0.50mol Cl ^–  

So 1 mol ions in total are produced (0.5 mol + 0.5 mol)

1 mol NaCl ions /0.25 = 4m NaCl

Where “m” is molal

1. Molarity of Calcium Chloride

55.5g CaCl₂ X 1 mole CaCl₂  / 111g X  3 mol ions/ 1 mol CaCl₂ = 1.5 mol CaCl₂ ions

0.5 mol CaCl₂  →   0.5 mol Ca²⁺  + 1.0 mol Cl ^–  

So 1.5 mol ions in total are produced (0.5 mol + 1.0 mol)

1.5 mole CaCl₂  ions / 0.25kg = 6 mCaCl₂

Where “m” is molal

1. Molarity of Sodium Chloride V Molarity of Calcium Chloride

The amount of ions generated determines the molarity of a substance

NaCl

1 mole NaCl ions / 0.25 kg = 4m NaCl

CaCl₂

1.5 mole CaCl₂ ions / 0.5 kg = 6 mCaCl₂

Temperature depression NaCl v CaCl₂

Temperature depression: change in temperature = k_f   X m

Where k_f is molal freezing point depression constant (1.86 ^o C/m for water)

NaCl

Change in temperature = k_f   X m

= 1.86 ^o C/ m X 4m

= 7.44 ^o C

CaCl₂

Change in temperature = k_f   X m

= 1.86 ^o C/ m X 6m

= 11.2 ^o C

Conclusions:

Through this experiment, the purpose was successfully met as students gained an understanding of molality and colligative properties. They learned how to calculate molality and observed the effects of different salts on the freezing point of ice. Additionally, they discovered the varying impacts of the salts on the melting point of ice cream, highlighting the practical applications of colligative properties in food preparation.

Notes:

Colligative properties, such as freezing point depression and osmotic pressure, are crucial in ice cream production. They help to lower the freezing point of the ice cream mixture, resulting in a smoother texture and preventing the formation of large ice crystals. This enhances the overall quality and palatability of the final product.

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This lab will be conducted by an experienced instructor. As you watch the lab, you should keep a lab notebook just as you would if you were personally conducting the lab. A well-kept lab notebook is the key to successful labs. The lab notebook acts as the record of your experiment, helps you organize your thoughts and understand the experiment’s results and is useful for writing your lab report. Your lab notebook and/or lab report can be used as you take the lab exam that accompanies each experiment.

To complete the lab report requirement, be sure to follow the “Lab Report Sample” as your model and type out your lab report using the “Lab Report Template”. These can be found under “Lab Overview”. You can upload your report by clicking “Submit,” and then attaching your document.