Final answer:
At equilibrium in an open container, where a cell is in balance with its surrounding 0.5M glucose solution and contains 0.6M glucose itself, the cell's pressure potential is zero since there are no net movement of water or external pressure affecting the cell.
Step-by-step explanation:
When a cell is in equilibrium with its surrounding solution, this suggests that the net movement of water across the cell membrane is zero. In such a scenario, the osmotic pressure within the cell must balance the osmotic pressure of the external solution. At equilibrium, the pressure potential (Ψp) of the cell is considered to be zero; this is because there is no net tendency for water to move into or out of the cell due to pressure differences. Also, considering that there are no pressure differences affecting the cell from atmospheric pressure or other external forces in an open container, the pressure potential remains at zero.