Question

Which inorganic precipitate acts as a semipermeable membrane?
a.) Calcium sulphate
b.) Barium oxalate
c.) Nickel phosphate
d.) Copper ferrocyanide

Answer 1

Hint: Out of the given four options, copper ferrocyanide (\[C{u_2}\left[ {Fe{{\left( {CN} \right)}_4}} \right]_{}^{}\]) has a little complex structure compared to the rest three of the compounds. A semipermeable membrane has complex structure too. Co-relating both, we can proceed with our solution.

Complete step-by-step answer:
A semipermeable membrane is considered to be a layer that only allows certain molecules to pass through. Semipermeable membranes can be of both biological and artificial types.
An example of a semi permeable membrane is the cell membrane in which it allows passage of only certain types of molecules via diffusion and also sometimes occasionally by facilitated diffusion.
Semi permeable can also be called by the following names –
selectively-permeable membrane, partially-permeable membrane and differentially-permeable membrane.
They are of two types of semi-permeable membranes – One being the natural semi-permeable membrane like vegetable membranes and animal membranes which are found just under the outer skin of the plants and animals. And the second type being the artificial semi permeable membrane like a parchment paper, cellophane and certain freshly prepared inorganic membranes.
Copper Ferrocyanide acts as a semipermeable membrane and it is an artificial semipermeable membrane. It is believed to contain large pores that are enough for the small molecules of water to get through but also at the same time too small to allow the larger molecules of sugar to pass.
It has been studied that the copper ferrocyanide membrane is made up from colloidal particles having diameters ranging from 50 to 400 μ and also the pores enclosed by these particles have an average diameter which are although large enough to allow passage to any non-colloidal molecule, are also small enough to be completely within the range of capillary effects.
Therefore, the correct option for the above question is option (D) ie Copper Ferrocyanide.

Note – Some of the synthesized or artificial semi-permeable membranes are copper ferrocyanide, calcium phosphate, cellulose nitrate any many more. Semi-permeable membrane of copper ferrocyanide is the one that is most widely used because of the fact that it can resist high pressure of about 150 atmospheres and is also very easy to prepare.