Which particles can pass through a semipermeable membrane?

Pickles have a long shelf life and do not get spoiled for months,why?

$0.05 \ M \ CuSO_4$ when treated with $0.01 \ M \ K_2Cr_2O_7$ gives a green coloured solution of $Cu_2Cr_2O_7$. In an osmosis setup with a Semi Permeable Membrane $(SPM)$ separating Side $X$ $(K_2Cr_2O_7)$ and Side $Y$ $(CuSO_4)$,determine the observation due to osmosis.

The swelling in feet and ankles of an aged person due to sitting continuously for long hours during travel,is reduced by soaking the feet in warm salt water. This is because of

The osmotic pressure of blood is $7.47 \, bar$ at $300 \, K$. To inject glucose to a patient intravenously,it has to be isotonic with blood. The concentration of glucose solution in $g \, L^{-1}$ is $......$ (Molar mass of glucose $= 180 \, g \, mol^{-1}$,$R = 0.083 \, L \, bar \, K^{-1} \, mol^{-1}$) (Nearest integer)

What is osmotic pressure? Explain and derive its equation.