Chapter 7, Problem 7.60AP

(a)

Interpretation Introduction

Interpretation:

The enthalpy for the formation of hydrogen chloride is whether exothermic or endothermic is to be determined.

Concept Introduction:

Enthalpy $\left(H\right)$: it is the total amount of heat in a particular system.

The value of heat formed in a reaction $\text{ΔH}$ is calculated by the formula,

$\text{ΔH=}{{\displaystyle \sum \left(BondDissociationEnergy\right)}}_{\left(\text{reactants}\right)}-{{\displaystyle \sum \left(BondDissociationEnergy\right)}}_{\left(\text{products}\right)}$

If the value obtained for $\text{ΔH}$ in a reaction is positive then it is an endothermic reaction whereas the value obtained for $\text{ΔH}$ is negative it is an exothermic reaction.

(b)

Interpretation Introduction

Interpretation:

At equilibrium the formation of hydrogen chloride is whether reaction or product favored is to be determined.

Concept Introduction:

Equilibrium constant: It is the ratio of products to reactants has a constant value when the reaction is in equilibrium at a certain temperature. And it is represented by the letter K.

For a reaction,

$\text{aA}\text{+}\text{bB}\rightleftarrows \text{cC}\text{+}\text{dD}$

The equilibrium constant is, $K=\frac{{\text{[C]}}^{\text{c}}{\text{[D]}}^{\text{d}}}{{\text{[A]}}^{\text{a}}{\text{[B]}}^{\text{b}}}$

where,

a, b, c and d are the stoichiometric coefficients of reactant and product in the reactions.

If $K<1$, then it is reactant favoured reaction whereas if $K>1$, then it is product favoured reaction.

(c)

Interpretation Introduction

Interpretation:

The effect on the equilibrium of each given changes in formation of hydrogen chloride is to be determined.

Concept Introduction:

Enthalpy $\left(H\right)$: It is the total amount of heat in a particular system.

If the value obtained for $\text{ΔH}$ in a reaction is positive then it is an endothermic reaction whereas the value obtained for $\text{ΔH}$ is negative it is an exothermic reaction.

Le Chatelier’s principle: If an equilibrium is disturbed by changing conditions, the system will moves the equilibrium to reverse the change.

Factor’s that effect chemical equilibria:

• Concentration – Equilibrium will be affected by changing the concentration of reactant or product. If we increase the concentration of reactant system will try to reverse the change by favoring forward reaction and thus increase the concentration of products. Likewise adding products increase yield of reactants.
• Temperature – When the temperature increases equilibrium will shift in the endothermic direction, in the direction that absorbs heat. When the temperature decreases equilibrium will shift in the exothermic direction, in the direction that releases heat.
• Pressure – If the reaction consists of only liquid and solid reactants and products, pressure has no effect in the equilibrium.

  In gas reactions if the number of moles has no change then there will be no effect by pressure on equilibrium.

  If pressure increases then equilibrium will shift to the direction having less number of molecules and if pressure decreases system will shift to the direction having more number of molecules.