Chemical Energetics

Methane reacts with chlorine to make chloromethane.

The reaction is exothermic.

Draw, on the axes provided in Fig. 6.1, the reaction pathway diagram for this reaction.

Include labels for the:

• axes
• reactants
• products
• enthalpy change of reaction, $\Delta H$
• activation energy, $E_a$.

Hydrogen iodide decomposes to make hydrogen and iodine.

Calculate the enthalpy change of this reaction.

Use the bond energies in Table 6.1.

Table 6.1

enthalpy change of reaction = ______ $\text{kJ / mol}$

Nitrogen reacts with oxygen to make nitrogen monoxide.

The reaction is endothermic.

Draw, on the axes provided in Fig. 6.1, the reaction pathway diagram for this reaction.

Include labels for the:

• axes
• reactants
• product
• enthalpy change of reaction, $\Delta H$
• activation energy, $E_a$.

Hydrogen reacts with bromine to make hydrogen bromide.

Calculate the enthalpy change of this reaction.

Use the bond energies in Table 6.1.

Table 6.1

enthalpy change of reaction = ______ $\text{kJ / mol}$

Complete the energy profile diagram for this reaction.

Label reactants, products and $\Delta H$.

Explain, in terms of bond breaking and bond forming, why the reaction is endothermic.

Explain, in terms of the energy changes that occur during bond breaking and bond making, why respiration is an exothermic reaction.

______

Complete the energy profile diagram for respiration.

On your diagram label the

• products,
• enthalpy change for the reaction, $\Delta H$,
• activation energy, $E_\text{a}$.

Table 3.1 shows some bond energies.

Table 3.1

Show by calculation that the enthalpy change of the reaction between methane and chlorine, $\Delta H$, is $-119\text{ kJ/mol}$.

Complete the reaction pathway diagram in Fig. 3.2 for the reaction between methane and chlorine.

Label the:

• reactants
• products
• enthalpy change of the reaction, $\Delta H$
• activation energy, $E_\text{a}$

Table 3.1 shows some bond energies.

Table 3.1

Show by calculation that the enthalpy change of the reaction between ethene and bromine, $\Delta H$, is $-107\text{ kJ / mol}$.

Complete the reaction pathway diagram in Fig. 3.2 for the reaction between ethene and bromine.

Label the:

• reactants
• product
• enthalpy change of the reaction, $\Delta H$
• activation energy, $E_a$.

Calculate the heat energy released when $25.0\text{ g}$ of hydrogen is completely combusted.

heat energy released = ______ $\text{kJ}$

Use ideas about bond breaking and bond forming to explain why this reaction is exothermic.

______

Explain, in terms of the energy changes that occur during bond breaking and bond making, why photosynthesis is an endothermic reaction.

______

Complete the energy profile diagram for photosynthesis.

On your diagram label the

• products,
• enthalpy change for the reaction, $\Delta H$,
• activation energy, $E_a$.

Use ideas about bond breaking and bond forming to explain why the decomposition of hydrogen peroxide is exothermic.

______

The energy profile diagram for the decomposition of hydrogen peroxide is shown.

Identify the energy changes.

change A = ______
change B = ______

Calculate the heat energy released when $600\text{ dm}^3$ of cyclobutane, at room temperature and pressure, is completely combusted.

heat energy = ______ $\text{kJ}$

Explain, in terms of the energy associated with bond breaking and bond making, why the combustion of cyclobutane is exothermic.