To stop the flow of water into Cell X when placed in a beaker of water, a pressure of 5psi must be applied. For Cell Z, subjected to the same conditions, a pressure of 13.5psi must be used. Which cell has the greatest solute concentration? Briefly explain.

Cell Z has the greatest solute concentration

Explanation:

The water moves from higher potential to lower potential. More the solute concentration in solution the lower will be water potential. External mechanical pressure increases the water potential.

Cell Z has more solute concentration, So it require more external pressure to equalize its internal water potential with external water potential for stopping the movement of water from high potential to lower potential.

Remember the maximum potential of water is zero at standard temperature and pressure.