Question

Experiment:

Add 1/8 test tube chlorobenzene and 1/4 test tube water to a 100mm test tube.

If the chlorobenzene rests on top of the water, tap the test tube to make it fall to the bottom.

Add 0.7 g of salt and stopper and rock until it all dissolves.

Let it stand for a minute to clear.

Questions:

1) Which layer is on the bottom? (from my experiment I got that chlorbenzene was at the bottom)

2) Explain why. (Which liquid dissolved the salt? Why? How did that change its density?)

Answer 1

Density of pure Chlorobenzene = 1.11 g/ml

Density of pure water = 1 g/ml

(1) Liquid having higher density will form lower layer. So When both liquids are mixed, Chlorobenzene will be at lower layer.

(2) Salt is polar compound like water. So it will mix into water layer.

Density of water will increase after salt dissolution.

Adding salt increases mass more than volume. hence density goes up.

Further adding extra fact, we know that swimming is easier in sea water than river water. It is because sea water contains dissolved salts which increases density of water.