Question

How can you remove the hard calcium carbonate layer of the egg without damaging its semiprermiable membrane? Can this egg be inserted into a bottle with a narrow neck without distorting its shape? Explain the process involved.

Answer 1

(i) When egg is placed in dilute mineral acid solution (preferably dilute \[\ce{HCl}\] solution), the hard external \[\ce{CaCO3}\] layer of the egg dissolves out/removed without damaging its semipermeable menbrane.

(ii) Yes, this egg can be inserted into a bottle with a narrow neck without distorting is shape.

This process invloved utilising phenomenon of osmosis is explained as below:

Egg is placed in mineral acid solution - after time egg is removed and placed in a hypertonic solution* - Size of the egg gradually decreases after some time and it shrivles due to osmasis. SInce the egg has shrivelled it can, now be inserted easily into a bottle with narrow mouth. The egg is, therefore, placed in a battle with narrow neck and then a hypotonic solution is filled into this bottle. On adding hypotonic solution**, egg regains shape due to osmosis.

• Hypertonic solution - is a solution with higher salt concentration than that of the normal body cells so that the solvent/water is drawn out of the cell by osmosis; or any solution with higher osmotic pressure than another solution is called "Hypertonic solution".

• Hypotonic solution is a solution with lower salt concentration than that of the normal body cells so that water/solvent flows into the cell by osmosis; or - hypotonic solution is a solution which has lower osmotic pressure than the other solution.