Chapter 5, Problem 31Q

Interpretation Introduction

Interpretation:

For the given decomposition reaction of ${\text{NH}}_{\text{3}}$ the volume of product gases is twice the volume of ${\text{NH}}_{\text{3}}$ at constant pressure and temperature should be explained, the increment of total pressure at constant volume and temperature after the completion reaction should be determine and explain the reason for increment and the comparison between the partial pressures of product gases and initial pressure of ${\text{NH}}_{\text{3}}$ should be determined.

Concept introduction:

• Balanced equation of a reaction is written according to law of conservation of mass.

• According to Avogadro’s law of gas molecules,

  If the number of moles of gases in a container is increased then the volume will increase at constant temperature and pressure.

  Equation for Avogadro’s law is,

  $\frac{{\text{V}}_{\text{initial}}}{{\text{n}}_{\text{initial}}}\text{=}\frac{{\text{V}}_{\text{final}}}{{\text{n}}_{\text{final}}}$

• According to ideal gas law: the pressure of gas is directly proportional to the number of moles of gas at constant volume and temperature.

$\frac{\text{P}}{\text{n}}\text{=}\frac{\text{RT}}{\text{V}}$, P and n are proportional.

Mathematically, for two gases (1 and 2) at constant V and T,

$\frac{{\text{P}}_{\text{1}}}{{\text{n}}_{\text{1}}}\text{=}\frac{{\text{P}}_{\text{2}}}{{\text{n}}_{\text{2}}}\Rightarrow \frac{{\text{P}}_{\text{1}}}{{\text{P}}_{\text{2}}}\text{=}\frac{{\text{n}}_{\text{1}}}{{\text{n}}_{\text{2}}}$

• Mole ratios between the reactant and products of a reaction are depends upon the coefficients of respective reactant in a balanced chemical equation.

• Partial pressure of a gas in a mixture of gases is the pressure of that gas when it alone.