in which kind of solution is the concentration of solutes the same inside and outside of the cell?

The cell is in an isotonic solution.

Quick Scoop

When the concentration of solutes is the same inside and outside the cell, the surrounding solution is called an isotonic solution.

In an isotonic solution, water still moves in and out of the cell, but there is no net movement of water, so the cell does not swell or shrink.

Tiny story to picture it

Imagine a cell like a person in a room where the number of people in the hallway and the room is equal.
The person can step in and out freely, but overall the crowd size in the room stays the same — that balance is like an isotonic environment for a cell.

TL;DR:
In which kind of solution is the concentration of solutes the same inside and outside of the cell?
→ An isotonic solution.

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