Chapter 8, Problem 1SAQ

What are the correct coefficients (reading from left to right) when the chemical equation is balanced?

  _PCI₃(/) + _H₂O(/) → _H₃PO₃(aq) + _HCl(aq)
1, 3,2,1
1_: 2, 1, 1
3, 6, 1,9
1: 3, 1, 3

Interpretation Introduction

Interpretation: To find out the correct coefficients when the chemical equation is balanced.

Concept introduction:

In chemistry, the coefficient is the number present in front of the chemical formula in a chemical equation.

Correct answer: The correct answer is option (d) $1,3,1,3$

Explanation of Solution

Reason for the correct answer: The unbalanced equation:

  ${\text{PCl}}_{\text{3}}(l)+{\text{H}}_{\text{2}}\text{O(}l\text{)}\to {\text{H}}_{\text{3}}{\text{PO}}_3(aq)+\text{HCl}(aq)$

  $1$ O atom   $3$ O atoms

To balance O atoms place the coefficients $3$ before ${\text{H}}_2\text{O}$

  ${\text{PCl}}_{\text{3}}(l)+3{\text{H}}_{\text{2}}\text{O(}l\text{)}\to {\text{H}}_{\text{3}}{\text{PO}}_3(aq)+\text{HCl}(aq)$

  $3$ Cl atoms  $1$ Cl atom

To balance Cl atoms place the coefficients $3$ before HCl

  ${\text{PCl}}_{\text{3}}(l)+3{\text{H}}_{\text{2}}\text{O(}l\text{)}\to {\text{H}}_{\text{3}}{\text{PO}}_3(aq)+3\text{HCl}(aq)$

This is the balanced equation because $1$ P, $3$ Cl, $6$ H and $3$ O atoms are present on both sides.

The correct coefficients from left to right in the balanced equation will be $1,3,1,3$ and the correct choice will be option (d).

Reason for incorrect answer: Option (a) coefficient $\text{1, 3, 2, 1}$ is not possible for the above mentioned balanced equation. Hence option (a) is wrong.

Option (b) coefficient $\text{1, 2, 1, 1}$ is not possible for the above mentioned balanced equation. Hence option (b) is wrong.

Option (c) coefficient $\text{3, 6, 1, 9}$ is not possible for the above mentioned balanced equation. Hence option (c) is wrong

Thus, option (d) is found to be correct answer and options (a), (b) and (c) found to be wrong answers.