White fumes appear around the bottle of anhydrous aluminium chloride. Give reason.

Which of the following statements is correct for boric acid?

Match the List-$I$ with List-$II$.

List-$I$ (Element)	List-$II$ (Application)
$A$. $Cs$	$I$. High temperature thermometer
$B$. $Ga$	$II$. Water repellent sprays
$C$. $B$	$III$. Photoelectric cells
$D$. $Si$	$IV$. Bullet proof vest

Choose the most appropriate answer from the options given below:

Select the incorrect statement:
$a$. $PCl_5$ forms a weak monobasic acid during hydrolysis.
$b$. In $B_3N_3H_6$,nucleophilic attack occurs on the $B$ atom.
$c$. $Al_2Cl_6$ is a polar and planar molecule.
$d$. In $AlF_3$,the hybridization of $Al$ is $sp^2$.

When metal $X$ is treated with sodium hydroxide,a white precipitate $(A)$ is obtained,which is soluble in excess of $NaOH$ to give soluble complex $(B)$. Compound $(A)$ is soluble in dilute $HCl$ to form compound $(C)$. The compound $(A)$ when heated strongly gives $(D)$,which is used to extract metal. Identify $(X), (A), (B), (C)$ and $(D)$. Write suitable equations to support their identities.

In a molecule of pyrophosphoric acid $(H_4P_2O_7)$,the number of $P-OH$,$P=O$ and $P-O-P$ bonds/moiety(ies) respectively are: