Question

$0.98\text{ }g$ of an acid (A) of phosphorus in $100\text{ }mL$ solution is $0.1\text{ }M$ and neutralizes $300$ mL of $0.1\text{ }N\text{ }NaOH$
$\left( A \right){\xrightarrow{\mathop{MgCl_2}}}\,\left( B \right){\xrightarrow{\mathop{\Delta}}}\,\left( C \right)$
If $1.11$ of $\left( C \right)$ is obtained from given $\left( A \right).$ Compounds (A), (B) and (C) are identified as: $A:{{H}_{3}}P{{O}_{4}},\text{ }B:MgHP{{O}_{4}}$ ​ and $C:M{{g}_{2}}{{P}_{2}}{{O}_{7}}$
​If true enter $1$ , else enter $0.$

Answer 1

Hint : We know that the oxidation number of an atom is the charge that results when the electrons in a covalent bond are assigned to the more electronegative atom. Oxidation state and oxidation number are quantities that commonly equal the same value for atoms in a molecule and are often used interchangeably.

Complete Step By Step Answer:
Let X be the molar mass of acid of phosphorus. The product of the molar mass and molarity is the amount in $g/L.$
$\therefore X\text{ }molarity=\text{ }g/L$
Hence, $X\text{ }0.1=\text{ }9.8g{{L}^{-1}}$
Molar mass of acid $=\text{ }98\text{ }g\text{ }mo{{l}^{~-1}},$ Let basicity of acid be $=\text{ }x,$ by converting the molarity of acid in normality of acid then $0.1$ M acid $=\left( 0.1\text{ }X\text{ } \right)\times N$
The amount of acid present is equal to the amount of the base neutralized.
$100\times \text{ }0.1\text{ }XX=300X\left( 0.1\text{ }N\text{ }NaOH \right)$ , Since we know that basicity $x=3$
Thus, acid is tribasic which is phosphoric acid., ${{H}_{3}}P{{O}_{4}}$ .
Hence, the compound A is ${{H}_{3}}P{{O}_{4}}$
The compound B is $MgHP{{O}_{4}}$
The compound C is $M{{g}_{2}}{{P}_{2}}{{O}_{7}}$
Now we just have to identify if C is confirmed by the following reaction: $2{{H}_{3}}P{{O}_{4}}\xrightarrow{{}}M{{g}_{2}}{{P}_{2}}{{O}_{7}}$
$2$ moles of A gives One mole of C.
Hence, $0.98\text{ }g$ of A will give $1.11\text{ }g$ of C.
Correct answer is 1.

Additional Information:
Most of the time, it doesn't matter if the term oxidation state or oxidation number is used. Oxidation state refers to the degree of oxidation of an atom in a molecule. Oxidation states are typically represented by integers, which can be positive, negative, or zero. In some cases, the average oxidation state of an element is a fraction, such as $8/3$ for iron in magnetite

Note :
Remember that Phosphorus belongs to the group $15.$ It has $5$ electrons in its valence shell. So it can either lose $5\text{ }e\text{ }-$ to attain +5 oxidation state or gain $3\text{ }e-$ to attain $-3$ oxidation state. Hence its oxidation state varies from $-3$ into $+5$ in ${{H}_{3}}P{{O}_{4}}.$