Three lab groups carried out an experiment to identify the correct molarities for five solutions. Each unknown contained one of
the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and 1.0 M. Each data entry represents the average of 3 sample replications of 1 cm3 sweet potato cubes expressed as percent change in mass after an overnight (24 hr) soak in the unknown solutions. From the data given, which statement most accurately describes what is occurring in response to a particular unknown solution.
B) Osmosis of water molecules from unknown solution A likely caused the increase in mass observed.
Explanation:
Osmosis is a type of <em>diffusion </em>(a random movement of molecules to an area of lower concentration from an area of higher concentration) of water. Like other molecules, water can pass through a cell membrane and it will diffuse across the membrane, along its own concentration gradient independent of other particles that could be present in solution. The concentration of water in a solution is <em>inversely </em>(opposite) related to the concentration of the solute, meaning that water will move from a region of high water potential to a region of lower water potential during osmosis.
Unknown solution A had the highest water potential with a sucrose concentration of 0.0 M. This means that water diffused through the membranes of the cells in the sweet potato cube as it moved along its own <em>concentration gradient</em> (from a region of high water potential to a region of lower water potential) causing an increase in the mass of the sweet potato cube
