5. Aluminium combines readily with both dry fluorine and dry chlorine. Anhydrous

Question

5. Aluminium combines readily with both dry fluorine and dry chlorine. Anhydrous aluminium chloride is a white solid which sublimes at about 200°C, it reacts with water and dissolves in non-polar solvents. Aluminium fluoride is a crystalline solid up to a temperature of 1290°C; it is insoluble in non-polar solvents. a. Explain how the electron-sea model accounts for the high electrical and thermal conductivity of aluminium b. Predict, using the information above only, the name of the bond type present in: c. Give an explanation for the difference in bond type present in the two anhydrous d. Predict whether anhydrous aluminium fluoride would have a low or a high melting anhydrous aluminium chloride, and anhydrous aluminium fluoride. aluminium halides based on your prediction for part b. temperature carefully explaining the reasons for your prediction.

Explanation / Answer

Electric conductivity in aluminium is because of very large no of free electrons,and electron sea model is called so because it says that metals have sea of electrons.thus this model accounts for high electrical conductivity of Al.

Thermal conductivity is by the vibration of electron.As from sea electron theory the no.of electrons are very high,thus vibrations are more and hence more is thermal conductivity of Al.

B):since electronegativity difference is very low between Al and Cl, therefore bond is covalent in Aluminium chloride.

Anhydrous Aluminium Floride has ionic bonding.

C):there is lesser electronegativity difference in 1 than in 2. Moreover there is repulsion due to small size of florine.

D):since AlF3 is ionic, therefore there is close packing,and thus the melting point is higher than AlCl3 having Covalent bond.

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