Question 1

Which of the following best explains why potassium permanganate diffuses faster than Janus Green in agar at the same temperature?

Accepted Answer

Potassium permanganate has a lower molecular mass, allowing it to move more rapidly through the agar matrix.

Question 2

A dialysis bag containing 10 ml of 10% sucrose is placed in a beaker of distilled water. After 40 minutes, the mass of the bag increases. Which process is responsible for this change, and what is the direction of water movement?

Accepted Answer

Osmosis; water moves from the beaker into the bag.

Question 3

In the experiment testing selective permeability, which molecule is least likely to diffuse out of the dialysis bag into the beaker, and why?

Accepted Answer

Starch, because its large molecular size prevents it from passing through the membrane.

Question 4

A sheep red blood cell is placed in a 10% NaCl solution. What will happen to the cell, and what is the underlying reason?

Accepted Answer

The cell will shrink (crenate) because water moves out of the cell into the hypertonic solution.

Question 5

Which of the following best describes the effect of temperature on the rate of diffusion, as observed in the dye diffusion experiment?

Accepted Answer

Increasing temperature increases the kinetic energy of molecules, resulting in a greater rate of diffusion.

Question 6

If a dialysis bag containing distilled water is placed in a beaker of 10% sucrose, what will happen to the mass of the bag after 40 minutes, and why?

Accepted Answer

The mass will decrease because water will move out of the bag into the hypertonic beaker solution.

Question 7

Which test would you use to detect the presence of reducing sugars in the beaker solution after dialysis, and what result indicates a positive test?

Accepted Answer

Add Benedict’s reagent and heat; a color change indicates a positive result.

Question 8

A plant cell (Elodea) is placed in a 20% NaCl solution. What is the expected observation under the microscope, and what is the process called?

Accepted Answer

The cell membrane pulls away from the cell wall (plasmolysis) due to water loss.

Question 9

Which of the following equations correctly represents the relationship between solute concentration and water potential ($$\Psi) in $$osmosis?

Accepted Answer

$$\Psi = \Psi_s + \Psi_p$$

Question 10

In the context of the dialysis bag experiments, which variable is the independent variable and which is the dependent variable?

Accepted Answer

Independent variable: solute concentration; Dependent variable: change in mass of the bag.

Question 11

If the molecular mass of a solute is increased, what is the expected effect on its rate of diffusion through agar, and why?

Accepted Answer

The rate of diffusion decreases because larger molecules move more slowly.

Question 12

A dialysis bag containing 10 ml of 10% sucrose is placed in a beaker of 10% sucrose. After 40 minutes, what is the expected net movement of water, and why?

Accepted Answer

There is no net movement of water because the solutions are isotonic.

Question 13

Which of the following best describes the property of the dialysis bag that allows some molecules to pass while restricting others?

Accepted Answer

Selective permeability

Question 14

In the experiment with sheep blood, what would you expect to observe microscopically when the cells are placed in 0.45% NaCl, and why?

Accepted Answer

Cells will swell and may burst (lyse) because water enters the cells in a hypotonic solution.

Question 15

Which hazardous chemical is used to test for the presence of chloride ions in the beaker solution, and what is the expected result if chloride is present?

Accepted Answer

Silver Nitrate; a milky-white precipitate forms.

Question 16

A student hypothesizes that if the temperature is decreased to 0°C, the rate of diffusion of Janus Green and Potassium Permanganate through agar will:

Accepted Answer

Decrease, because lower temperature reduces molecular kinetic energy.

Question 17

Which of the following statements about osmosis in plant cells is correct?

Accepted Answer

Osmosis occurs in plant cells, and the presence of a cell wall allows the cell to become turgid without bursting.

Question 18

In the context of the experiments described, which of the following best defines a hypertonic solution?

Accepted Answer

A solution with a higher solute concentration than the cell or bag, causing water to move out.

Question 19

If a mixture of molecules is placed in a dialysis bag, which factor most strongly determines whether a molecule will diffuse through the membrane?

Accepted Answer

The size of the molecule relative to the pore size of the membrane.

Diffusion and Osmosis: Principles, Experiments, and Cellular Effects

Guida di studio - Domande di pratica

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