The set-up below was used to prepare anhydrous chlorides of elements in laboratory where no fume cupboard was available. The chlorides were to be collected in flask 1.

The set-up below was used to prepare anhydrous chlorides of elements in laboratory where no fume cupboard was available. The chlorides were to be collected in flask 1.

The following table shows the melting and boiling points of the chlorides that were prepared.
a) Explain why it is necessary to pass dry chlorine through the apparatus before heating each element.
b) Give two reasons why tubes II and III were filled with soda lime (solid mixture of sodium hydroxide and calcium hydroxide)
c) Explain why it would not be possible to collect any sodium chloride in flask 1
d) Name one other substance that can be used in tubes II and III
e) Write an equation for the reaction that forms phosphorous (III) chloride
f) Describe how you would separate a mixture of sodium chloride and aluminium chloride

Answers

a) Remove oxygen which could react with the element to form an oxide

b) i) Absorbs excess chlorine

ii) Absorbs moisture from the air hence prevent deliquescent chlorides from forming solutions

c) Sodium chloride has a high melting point and the burner flame, temperature is not able to vaporize
sodium chloride

d) Anhydrous calcium chloride

e) P_4(s) + 6Cl_2(g) $\rightarrow$ 4PCl_3(l)

f) – Heat the mixture
- Aluminium chloride sublimes while sodium chloride is left in the vessel
- Cool to obtain aluminium chloride

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johnmulu answered the question on April 10, 2017 at 10:08

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