Compounds of phosphorus - pcl3 - class-XII

A translucent white waxy solid (A) reacts with excess of chlorine to give a yellowish white powder (B). Here B is $PCl _5$.$PCl _5$ reacts with organic compounds containing -OH group converting them into chloro derivative $POCl _3. $.$PCl _5$ on hydrolysis gives (C).C is $POCl _3$ and is finally $POCl _3$ converted to phosphoric acid.

So  (A), (B) and (C) are $P _{4}$,$PCl _{5}$,$POCl _{3}$.

Hence option C is correct.

White P is reactive due to strain.
$P _{4}+6Cl _{2}\ \to \ 4PCl _{3}$
(White P)

All have dimer forms

$NO$ as $N _{2}O _{2}$

$NO _{2}$ as $N _{2}O _{4}$

$P _{2}O _{3}$ as $P _{4}O _{6}$

The oxidation state of ${P}$ in ${P}{Cl} _{3}$ is ${+3}$.
Each Chlorine atom has an oxidation number of ${-1}$. There are three chlorine atoms, hence the total oxidation number of the Chloride ions in ${-3}$. ${PCl} _{3}$ molecule is neutral. Hence the oxidation number of Phosphorus should be ${+3}$

The boiling point of ${PCl} _{3}$ is ${76.1}^{o}$ ${C}$

The hybridization of ${PCl} _{3}$ is ${sp}^{3}$. Phosphorus has five electrons in its outermost shell. Thus it forms three sigma bonds with three neighbouring Chlorine atoms. The remaining two electrons remain as a lone pair on Phosphorus atom. Thus these three sigma bonds and one lone pair, make this molecule ${sp}^{3}$ hybridized.

$PCl _3$ is a polar covalent molecule. It is polar because chlorine atoms are more electronegative than phosphorus atom and hence the polartity of the molecule is towards Chlorine atoms.
It is covalent because, Phosphorus has ive electrons in its outermost shell. It requires three more to complete its octet. Each chlorine atom has seven electrons in their outermost shell, they all require one electron each to complete their octet. Thus both phosphorus and chlorine complete their octet by mutually sharing their electrons. Hence this molecule is polar covalent in nature.

During the indusrial preparation of ${PCl} _{3}$, ${PCl} _{5}$ or Phosphorus Pentachloride is produced as an impurity. The balanced equation can be written as-
${PCl} _{3}$ ${+}$ ${Cl} _{2}$ ${=}$ ${PCl} _{5}$
Thus this impurity formation can be stopped by continual removal of ${PCl} _{3}$ as it is formed.

$PCl _3$ on hydrolysis gives $HCl$ and $H _3PO _3$.

$PBr _{3}+3H _{2}O\ \to \ H _{3}PO _{4}+HBr$
HBr is covalent $H _{3}PO _{4}$ is ionic. Solution conducts electricity due to ions.
So aqueous solution of $PBr _{3}$ conducts electricity due to presence of $H _{3}PO _{4}$.

The correct chemical equation is :

Solution:-
$PCl _3+3H _2O\rightarrow H _3\ PO _3+3HCl$

 Hydrolysis of $PCl _3$ gives:

Due to low ignition temperature of white phosphorus, it undergoes oxidation in presence of air which slowly raises its temperature and after a few moments it catches fire spontaneously. Due to this reason, it is stored under water. Ignition temperature ofred phosphorus is high Black phosphorus is crystalline in nature. Phosphorus forms a number of hydrides

${P}{Cl} _{3}$ is a colorless liquid or has a slight yellow color (but not bright yellow).

Phosphorus trichloride is prepared from phosphorus and chlorine. It has a pungent and irritating odour that is similar to that of hydrochloric acid.

The density of phosphorus trichloride is ${1.57}$ ${gm}{/}{cm}^{3}$

In ${ PCl } _{ 3 }$, $P$ is ${ sp }^{ 3 }$ hybridized with a lone pair. This makes its structure trigonal pyramidal. So, the correct answer is option $A$.

${PCl} _{3}$ is liquid under normal conditions. ${PCl} _{3}$ is a covalent compound. Phosphorus and each of the chlorine atoms fulfil their octet by mutually sharing their valence electrons. In general, covalent compounds have weak bond energy and hence they form liquid.

Dehydrated phosphorus trichloride in water gives phosphoric acid.

$PCl _3 + 3H _2O\rightarrow  H _3PO _3 + 3 HCl$

Hence option A is correct.