Osmosis and Diffusion

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Osmosis and Diffusion Osmosis and Diffusion A solution has a lot of properties. A substance in dilute solution behaves like a gas and the osmotic pressure of a substance in dilute solution is the same as it would exert if present as gas in the same volume as that occupied by the solution. So, the solute particles in dilute solutions play the same part as is played by the gas molecule in a gas. The osmotic pressure, pressure due to osmosis, was considered to be in analogue with the gas pressure. Van't Hoff was able to show that there is a close parallel between the pressure exerted by a gas and the osmotic pressure developed by a dilute solution. Due to the greater understanding of this concept of Osmosis and diffusion, this process, and the related processes have been put into use in many day to day applications. What is Diffusion and Osmosis? Just as a gaseous molecules of one gas can diffuse into a vacant space or into another gas, a solute can diffuse into the pure solvent from a solution as well.

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When we use saturated aqueous solution of KMnO4 through a thistle funnel into a water beaker, it starts forming a separate layer at the bottom. After a while the KMnO4 starts dissolving into the water by diffusion. This process continues until a homogenous solution is obtained. Hence, the diffusion of any solute can also take place when two solutions of unequal concentrations are kept in same vessel or in contact. Solvent molecules will always pass from dilute to the concentrated solution or lower concentration to higher concentration while solute particles will pass from the higher concentration to the dilute solution until an uniform concentration is achieved. Let us now consider a solution of salt contained in an inverted thistle funnel, the lower end of which is closed by a parchment paper. The parchment paper acts as a "semipermeable membrane", or a membrane which allows free passage to the solvent molecules, but not to the solute particles. If this salt solution is kept in contact with pure water in a vessel, the pure water from the vessel will start percolating through the semipermeable membrane in to the salt solution. Is Osmosis a Type of Diffusion? We know that, in diffusion, the solute molecules, and the solvent molecules move to equalize the concentration. And also, diffusion can occur when the solutions are in contact with each other. In osmosis, we see the movement of solvent particles, though not the solute particles. But, they again move through a semipermeable membrane, again to achieve an equilibrium concentration. So, we can safely say that, though there is a difference, osmosis can be called a type of diffusion.

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Osmosis is a type of diffusion, because here too, solvent move and an equilibrium concentration is reached. Compare and Contrast Osmosis and Diffusion :Osmosis and diffusion are similar in many respect. Both the phenomenon leads to equalizing the concentration of two solutions, in contact with each other. Thus, osmosis is a type of diffusion. Difference Between Osmosis and Diffusion :Though the basic idea behind the phenomenon of osmosis and diffusion is the same, there are a few differences. The solvent particles move from higher concentration to lower concentration. Also, the movement of solvent particles takes place with the help of a semipermeable membrane, which does not allow the solute to pass through.

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