Chapter 8, Problem 8.133MP

(a)

Interpretation Introduction

Interpretation:

Electron dot structure of hydrazine has to be drawn.  The geometry around each Nitrogen atom and its hybridization have to be predicted.

Concept Introduction:

Lewis electron dot structure is also simply known as electron dot structure which represents the reactive electrons and bonding in a compound.

VSEPR theory constitutes a set of rules which predicts the shape of the molecule based on the orientation of bonding and non-bonding electrons in the molecule.

(b)

Interpretation Introduction

Interpretation:

$\Delta H°$ for the combustion reaction of hydrazine has to be calculated using the given information and Hess’s law.

Concept Introduction:

Hess’s law is applied to calculate the enthalpy changes in a reaction.  According to Hess’s law –

“The overall enthalpy change of a reaction is equal to the sum of the enthalpy changes involving in each and every individual steps in the reaction.”

Thus if a reaction involves ‘n’ steps then enthalpy change $\Delta H°$ of the reaction is,

$\Delta H°=\Delta {\text{H}}_1^{°}+\Delta {\text{H}}_2^{°}+\Delta {\text{H}}_3^{°}\mathrm{....}+\Delta {\text{H}}_n^{°}$

(c)

Interpretation Introduction

Interpretation:

The amount of heat released on combustion of $100.0g$ of hydrazine has to be calculated.

Concept Introduction:

Heat liberated or absorbed during the reaction is,

$q=\Delta H\times n$

Where,

$q=heat\text{ liberated or absorbed}\text{. n = no}\text{.of moles of the substance}$

If sign of ‘q’ is negative it implies heat is liberated.  If sign of ‘q’ is positive it implies heat is absorbed.