Question

(a) Draw Lewis diagrams for${\mathbf{O}}_{\mathbf{2}}\mathbf{,}{\mathbf{CO}}_{\mathbf{2}}\mathbf{,}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\mathbf{,}{\mathbf{CH}}_{\mathbf{4}}\mathbf{,}{\mathbf{C}}_{\mathbf{8}}{\mathbf{H}}_{\mathbf{18}}\mathbf{and} {\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{5}}\mathbf{OH}$. In${\mathbf{C}}_{\mathbf{8}}{\mathbf{H}}_{\mathbf{18}}$, the eight carbon atoms form a chain with single bonds; in${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{5}}\mathbf{OH}$, the two carbon atoms are bonded to one another. Using average bond enthalpies from Table 12.5, compute the enthalpy change in each of the following reactions, if 1 mol of each carbon compound is burned, and all reactants and products are in the gas phase.

(b)${\mathbf{CH}}_{\mathbf{4}}\mathbf{+}\mathbf{2}{\mathbf{O}}_{\mathbf{2}}\to {\mathbf{CO}}_{\mathbf{2}}\mathbf{+}\mathbf{2}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$(burning methane, or natural gas)

(c)${\mathbf{C}}_{\mathbf{8}}{\mathbf{H}}_{\mathbf{18}}\mathbf{+}\frac{\mathbf{25}}{\mathbf{2}}{\mathbf{O}}_{\mathbf{2}}\to \mathbf{8}{\mathbf{CO}}_{\mathbf{2}}\mathbf{+}\mathbf{9}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$(burning octane, in gasoline)

(d)${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{5}}\mathbf{OH}\mathbf{+}\mathbf{3}{\mathbf{O}}_{\mathbf{2}}\to \mathbf{2}{\mathbf{CO}}_{\mathbf{2}}\mathbf{+}\mathbf{3}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$(burning ethanol, in gasohol)

Short answer

Subpart (a) Lewis structures of $O_2,C{O}_2,H_{2}O,C{H}_4,C_{18}{H}_{18}and{C}_2{H}_{5}OH$

$O_2$

$C{O}_2$

$H_{2}O$

$C{H}_4$

$C_{18}{H}_{18}$

$C_2{H}_{5}OH$

Step-by-step solution

Given

The Lewis diagrams are drawn and the enthalpies of the given reaction are calculated by using the enthalpies of the reactant and products.

Lewis Structure

The arrangement of electrons around the individual atom of a molecule is shown by Lewis’s structure. Lewis’s structure is represented in a very simplified form which shows the valence shell electron in a molecule.

Explanation

The Lewis diagram for the following is:

$O_2$

$C{O}_2$

$H_{2}O$

$C{H}_4$

$C_{18}{H}_{18}$

$C_2{H}_{5}OH$

The valency of hydrogen is one, oxygen is six, and that of carbon is four.