The table shows the mass of a potato cylinder in different salt solutions. The mass change is +4% at 0.0 M, 0% at 0.2 M, and −6% at 0.4 M. At which concentration is the cell sap closest to isotonic with the solution?
Answer and explanation
Correct answer: B. 0.2 M
- Step 1: Isotonic means no net water movement.
- Step 2: 0% change in mass occurs at 0.2 M, so the cell sap matches that concentration.
Answer
0.2 M.
Why not the others: 0.0 M: the cylinder gained mass so the solution is more dilute than the cells. 0.4 M: the cylinder lost mass so the solution is stronger than the cells. It cannot be estimated: there is a point with 0% change.
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