Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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hydrogen peroxide : H2O2
hydrochloric acid : HCl
ferrous sulfate : FeSO4 . 7H2O
sodium hydroxide : NaOH
sulphur : S8
methyl ethyl ketone : CH3 CO CH2 CH3
acetone : CH3 CO CH3
Class:
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elem=C,S
organic
Summary:
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Acetone reacts with sulphur in strongly alkaline environments. What products
are formed?
A similar reaction is observed between methyl ethyl ketone and sulphur.
Description:
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Sequence 1:
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Add some solid sulphur (flowers of sulphur) to a few ml of acetone: The solid
quickly goes to the bottom of the test tube. It does not dissolve appreciably.
Add some solid NaOH: The liquid becomes yellow, the pearls of NaOH remain on
the bottom. Only a very small part of the solid dissolves.
Add some water (the volume of water added is approximately half the volume
of acetone): Initially, the water mixes with the acetone and a yellow liquid
is formed. In the meantime, part of the solid NaOH dissolves and when more
of the NaOH is dissolved, then two liquids separate from each other. A yellow
water-layer is formed at the bottom and a dark brown acetone layer is formed
on top of the water-layer. A strong unpleasant smell is observed, definitely
not the smell of plain acetone.
Add much more water: Now the liquids mix again and one clear yellow liquid
is formed. All NaOH now quickly dissolves. The sulphur remains solid, at
the bottom of the test tube.
Add a solution of ferrous sulphate: Formation of a thick black precipitate,
consisting of fairly large flakes/particles.
Add a mix of HCl and H2O2 (50-50 mixture of HCl (10%) and H2O2 (3%)): The
black precipitate dissolves, the liquid becomes milk-like pale-yellow. A
faint odour of H2S is observed.
Sequence 2:
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Add some solid sulphur (flowers of sulphur) to a few ml of MEK: The solid
quickly goes to the bottom of the test tube. It does not dissolve appreciably.
Add some solid NaOH: The liquid remains colourless, the pearls of NaOH remain
on the bottom. The solid does not dissolve.
Add some water (the volume of water added is approximately half the volume
of MEK): The liquids do not mix (not even initially). All of the NaOH
dissolves in the water layer. The water layer (on the bottom) becomes yellow,
the MEK-layer becomes yellow/brown. The color of the MEK-layer is much less
intense than the color of the acetone-layer in this step of the experiment.
A strong and very unpleasant smell is observed, definitely not the smell
of MEK. This smell resembles the smell, observed in sequence 1 at this step
of the experiment.
Add much more water: The MEK layer dissolves in the water, the liquid becomes
yellow/brown (now it is slightly darker than the liquid of sequence 1 in this
step of the experiment). The liquid does not becomes completely clear. It
looks as if a finely divided suspension is formed of a liquid in the water.
Probably this is MEK, which is not completely dissolved in the water (MEK
cannot be mixed with water in all proportions like acetone).