Subjective Type

Aluminium trifluoride is insoluble in anhydrous HF but dissolves on addition of NaF. Aluminium trifluoride precipitates out of the resulting solution when gaseous BF3 is bubbled through. Give reasons.

Solution

Anhydrous HF is a covalent compound and forms strong intramolecular H bonds. It does not give fluoride ions and cannot dissolve $$\displaystyle AlF_3$$ in it. KF is an ionic compound and contains fluoride ions. It combines with $$\displaystyle AlF_3 $$ to form the soluble complex.
$$\displaystyle AlF_3+3NaF \rightarrow Na_3[AlF_6]$$
B has small size and high electronegativity. It has mauch higher tendency for complex formation than Al. Hence, when $$\displaystyle BF_3 $$ is added to above solution, $$\displaystyle AlF_3 $$ is precipitated.
$$\displaystyle Na_3[AlF_6] + 3BF_3 \rightarrow 3Na{BF_4} + AlF_3 $$

SIMILAR QUESTIONS

p - block Elements

Thallous chloride is more stable than Thallic chloride because of

p - block Elements

Anhydrous $$AlCl_{3}$$ is covalent but hydrated $$AlCl_{3}.6H_{2}O$$ is ionic because:

p - block Elements

Which of the following is not an ionic trihalide?

p - block Elements

How can you explain higher stability of BCl3 as compared to TlCl3?

p - block Elements

What are electron deficient compounds ? Are BCl3 and SiCl4 electron deficient species? Explain.

p - block Elements

BF3 is used as a catalyst in various organic reactions because ?

p - block Elements

Back bonding in $${ BF } _{ 3 }$$ does not affect :

p - block Elements

Aluminium (III) Chloride forms a dimer because

p - block Elements

Which of the following statements about anhydrous aluminium chloride is correct?

p - block Elements

Which is true for an element present in group 13 of the periodic table?

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