Experiment 12: Colloids (Part A)

Summary

This script outlines a chemistry experiment involving colloids, where a dialysis bag is used to separate components in a solution. The process begins with preparing the dialysis bag by tying it to a stir rod and filling it with starch and sodium chloride solutions. The bag is then submerged in deionized water for half an hour to allow diffusion. After removing the bag, the solution from the beaker is tested for starch and sodium chloride presence using iodine and silver nitrate reagents, respectively, in a series of test tubes.

Takeaways

• 🧪 Start by preparing a dialysis bag, ensuring it is wet and loose for easy handling.
• 🪢 Tie one end of the bag with a string to create a seal.
• 🗑 Insert a funnel into the bag to facilitate the addition of solutions.
• 📐 Add 10 mL of 1% starch solution and 10 mL of 1% sodium chloride solution into the bag.
• 🔗 Secure the other end of the bag and attach it to a stir rod for hanging.
• 🥣 Place 50 mL of distilled water into a 400 mL beaker and immerse the dialysis bag, allowing it to sit for 30 minutes.
• ⏳ Wait for the dialysis process to complete, which will separate the contents of the bag from the beaker's water.
• 🗑 Discard the contents of the dialysis bag and retain the solution in the beaker.
• 🧫 Transfer 5 mL of the beaker's solution into two separate test tubes for further testing.
• 🧪 Perform the iodine test on the 1% starch solution and the solution from the beaker using iodine reagent.
• 🧪 Conduct a silver nitrate test on the 1% sodium chloride solution and the solution from the beaker to observe reactions.
• 🔬 The experiment aims to demonstrate the dialysis process and the reactions of starch and sodium chloride with iodine and silver nitrate, respectively.

Q & A

What is the purpose of using a dialysis bag in the described experiment?

The dialysis bag is used to separate molecules of different sizes, allowing smaller molecules to pass through while retaining larger ones, which is essential in the study of colloids.

Why is the dialysis bag worked loose with fingers before tying it?

Working the dialysis bag loose ensures that there are no air bubbles trapped inside, which could interfere with the diffusion process during the experiment.

What is the role of the string in the experiment?

The string is used to tie the dialysis bag, securing the contents inside and preventing them from mixing with the external solution.

How much starch solution and sodium chloride solution are added to the dialysis bag?

10 milliliters of each, a 1% starch solution and a 1% sodium chloride solution, are added to the dialysis bag.

Why is the dialysis bag tied to a stir rod?

Tying the dialysis bag to a stir rod allows it to hang and be fully submerged in the beaker, facilitating the diffusion process.

What volume of di water is added to the beaker before placing the dialysis bag inside?

50 milliliters of di water are added to the 400-milliliter beaker.

How long is the dialysis bag left to sit in the beaker of di water?

The dialysis bag is left to sit for half an hour to allow sufficient time for diffusion.

Why is the solution from the dialysis bag discarded after the experiment?

The solution inside the dialysis bag is not needed for the subsequent tests, and the focus is on what has diffused into the beaker.

What is the purpose of the ten doll test performed on the test tubes?

The ten doll test is likely a typographical error; it should be the 'Tollen's test,' which is used to detect the presence of aldehydes. However, in this context, it seems to be a reference to observing reactions with iodine and silver nitrate reagents.

What reagents are added to test tubes one and two, and what is the purpose?

One drop of iodine reagent is added to both test tubes one and two. This is to observe any color change that would indicate the presence of starch or a reaction with the solution from the dialysis bag.

What is the significance of adding silver nitrate to test tubes three and four?

Adding silver nitrate to test tubes three and four is to test for the presence of chloride ions, as silver nitrate reacts with chloride to form a white precipitate of silver chloride.