Question

POST-LAB QUESTIONS / HOMEWORK 1. A student performed the following osmosis experiment, similar to the one you did, using a different combination of substances. Determine his/her results and explain them by answering the questions in the table by filling in the blank boxes. Assume that the dialysis bag is impermeable to sucrose. Set-up 1 Set-up 2 Set-up 3 Set-up 4 Set-up 5 Bags 15 mL in each Tap water Tap water 55% sucrose 21% sucrose solution solution Tap water Beakers Fill to cover the bag Tap water 12% sucrose 25% sucrose 43% sucrose 0.9% NaCl solution solution solution solution Does the bag weight stay the same, increase or decrease? Is the fluid in the beaker isotonic, hypotonic or hypertonic to the fluid in the bag? 2. a. Describe why substances move in the process of diffusion. b. In the diffusion experiment with potassium permanganate, did the water molecules move? Yes or no, and explain. 7 | Diffusion and Osmosis Post-Lab / Homework

Answer 1

Setup 1

The bag weight will remain the same. Because there is water in both beaker and bag. There won't be any net movement of water across the bag.

The fluid is isotonic.

Setup 2

Here there will be movement of water fro bag to the beaker. So the weight of the bag will decrease.

The solution is hypertonic.

Setup 3

Weight of the bag will increase

The solution is hypotonic.

Setup 4

Weight of bag will decrease

The solution is hypertonic

Setup 5

Weight of bag will decrease

The solution of hypertonic

2. a) Diffusion is a process by which molecules move from regions of higher concentration to regions of lower concentration. This is why we can feel the smell of food, perfumes, etc.

b) When a solution containing potassium is taken in a semipermeable bag and placed in a beaker with water, there will movement of water into the bag.

3. Selective permeability is a property of the membrane that allows only certain molecules to enter and exit. The cell membrane is a selectively permeable membrane.

4.a) Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration. This involves both solute and solvent

Osmosis is a type of diffusion. But it only involves solvent molecules and the movement takes place through a semi-permeable membrane.

b)

Diffusion

5)

Osmometer is used to measure the osmotic strength of a solution. Here the solvents move due to the osmotic pressure.

6)

This is because, compared to the cells of the leaves, the salt solution is hypertonic in nature. So there will be a movement of water from cells to outside. Thus the leaves become wilted.

7) Yes. The rate of osmosis will be more in setup 5