Methane reacts with chlorine in a substitution reaction.

$CH_4(g)+Cl_2(g) \to CH_3Cl(g)+HCl(g)$

The table gives average bond enthalpy data for the bonds involved.

A student uses average bond enthalpy data to estimate $\Delta H$ for the combustion of liquid ethanol. The experimental value is more exothermic than the estimated value.

A reaction can occur directly from $A$ to $B$, or by a two-step route through an intermediate $C$.

$A \to C \qquad \Delta H_1=-84\ \text{kJ mol}^{-1}$

$C \to B \qquad \Delta H_2=+27\ \text{kJ mol}^{-1}$

The carbon-halogen bond affects the rate of nucleophilic substitution in halogenoalkanes. The table gives bond length and bond enthalpy data for three carbon-halogen bonds.

Ethene can be hydrogenated to ethane.

$C_2H_4(g)+H_2(g) \to C_2H_6(g)$

The table gives standard enthalpy changes of combustion.

Nitrogen monoxide reacts with oxygen to form nitrogen dioxide.

$2NO(g)+O_2(g) \to 2NO_2(g)$

The table gives standard enthalpy changes of formation.

The lattice enthalpy of $MgO$ is much larger than that of $NaCl$ when both are defined as the energy required to separate the solid into gaseous ions.

A series of halogenoalkanes, $CH_3X$, undergoes nucleophilic substitution with hydroxide ions. Data for the carbon-halogen bond and the relative initial rate are shown.

Chloromethane can be produced by the reaction of methane with chlorine:

$CH_4(g) + Cl_2(g) \to CH_3Cl(g) + HCl(g)$

Average bond enthalpy data are provided.

Standard enthalpies of formation data are given in the table.

Carbon monoxide can be formed from carbon and oxygen.

$C(s,\text{ graphite})+O_2(g) \to CO_2(g) \qquad \Delta H=-394\ \text{kJ mol}^{-1}$

$CO(g)+\frac{1}{2}O_2(g) \to CO_2(g) \qquad \Delta H=-283\ \text{kJ mol}^{-1}$

The data refer to a Born-Haber cycle for the formation of $NaCl(s)$ from $Na(s)$ and $\frac{1}{2}Cl_2(g)$. Lattice enthalpy is defined as the enthalpy change when one mole of ionic solid is separated into gaseous ions.

Ethene reacts with hydrogen chloride to form chloroethane. Average bond enthalpy data and the displayed formulae for the reactants and product are provided.

A reaction from A to B can occur directly or through an intermediate C. An enthalpy cycle and two enthalpy changes are shown.

Standard enthalpy of formation data are provided for ethanol and its complete combustion products at 298 K and 100 kPa.

Propene can be hydrogenated to propane:

$C_3H_6(g) + H_2(g) \to C_3H_8(g)$

Standard enthalpies of combustion are shown.

Limestone contains calcium carbonate, which decomposes on strong heating:

$CaCO_3(s) \to CaO(s) + CO_2(g)$

Standard enthalpy of formation data are shown.

Graphite and diamond are allotropes of carbon. Their standard enthalpies of combustion to $CO_2(g)$ are shown.

The Born-Haber cycle for $MgO(s)$ includes atomization of magnesium, atomization of oxygen, the first and second ionization energies of magnesium, the first and second electron affinities of oxygen, and lattice enthalpy of formation.

Lattice enthalpy is defined as:

$Mg^{2+}(g)+O^{2-}(g) \to MgO(s)$

The thermal decomposition of magnesium carbonate is difficult to measure directly. Two reactions with hydrochloric acid were measured in a calorimeter and used in a Hess cycle.

A Born-Haber cycle for sodium chloride is shown. In this course, lattice enthalpy is defined as the enthalpy change when one mole of ionic solid is separated into gaseous ions.

Hydrogen chloride can be formed from hydrogen and chlorine.

$H_2(g) + Cl_2(g) \to 2HCl(g)$

Average bond enthalpies are: $H-H = 436\ \text{kJ mol}^{-1}$, $Cl-Cl = 242\ \text{kJ mol}^{-1}$ and $H-Cl = 431\ \text{kJ mol}^{-1}$.

Ethene reacts with hydrogen bromide to form bromoethane.

$CH_2{=}CH_2(g) + HBr(g) \to CH_3CH_2Br(g)$

Average bond enthalpies are: $C{=}C = 614\ \text{kJ mol}^{-1}$, $H-Br = 366\ \text{kJ mol}^{-1}$, $C-C = 346\ \text{kJ mol}^{-1}$, $C-H = 414\ \text{kJ mol}^{-1}$ and $C-Br = 276\ \text{kJ mol}^{-1}$.

The enthalpy change for converting carbon monoxide to carbon dioxide can be found indirectly.

$CO(g) + \frac{1}{2}O_2(g) \to CO_2(g)$

Given:

$C(s,\text{ graphite}) + \frac{1}{2}O_2(g) \to CO(g)$, $\Delta H = -111\ \text{kJ mol}^{-1}$

$C(s,\text{ graphite}) + O_2(g) \to CO_2(g)$, $\Delta H = -394\ \text{kJ mol}^{-1}$

A Born-Haber cycle for magnesium oxide is shown. The lattice enthalpy is defined as the enthalpy change for $MgO(s) \to Mg^{2+}(g) + O^{2-}(g)$.

The rate of nucleophilic substitution of halogenoalkanes is affected by the strength of the carbon-halogen bond. The average bond enthalpies are shown.

$C-Cl = 338\ \text{kJ mol}^{-1}$, $C-Br = 276\ \text{kJ mol}^{-1}$, $C-I = 238\ \text{kJ mol}^{-1}$.

A student investigates the enthalpy change of decomposition of hydrated copper(II) sulfate using two measured hydration reactions.

Reaction 1: $CuSO_4(s) + aq \to CuSO_4(aq)$, $\Delta H_1 = -66.1\ \text{kJ mol}^{-1}$

Reaction 2: $CuSO_4\cdot 5H_2O(s) + aq \to CuSO_4(aq) + 5H_2O(l)$, $\Delta H_2 = +11.7\ \text{kJ mol}^{-1}$

Target reaction: $CuSO_4\cdot 5H_2O(s) \to CuSO_4(s) + 5H_2O(l)$

Methanol combusts according to the equation:

$CH_3OH(g) + \frac{3}{2}O_2(g) \to CO_2(g) + 2H_2O(g)$

Average bond enthalpies are: $C-H = 414\ \text{kJ mol}^{-1}$, $C-O = 358\ \text{kJ mol}^{-1}$, $O-H = 463\ \text{kJ mol}^{-1}$, $O{=}O = 498\ \text{kJ mol}^{-1}$ and $C{=}O$ in $CO_2 = 804\ \text{kJ mol}^{-1}$.

Propanone, $CH_3COCH_3(l)$, is a volatile solvent. The equation for its complete combustion under standard conditions is:

$CH_3COCH_3(l) + 4O_2(g) \to 3CO_2(g) + 3H_2O(l)$

Standard enthalpies of formation are: $\Delta H_f^\ominus[CH_3COCH_3(l)] = -249\ \text{kJ mol}^{-1}$, $\Delta H_f^\ominus[CO_2(g)] = -394\ \text{kJ mol}^{-1}$ and $\Delta H_f^\ominus[H_2O(l)] = -286\ \text{kJ mol}^{-1}$.

Ethene can be hydrogenated to ethane.

$C_2H_4(g) + H_2(g) \to C_2H_6(g)$

Standard enthalpies of combustion are: $\Delta H_c^\ominus[C_2H_4(g)] = -1411\ \text{kJ mol}^{-1}$, $\Delta H_c^\ominus[H_2(g)] = -286\ \text{kJ mol}^{-1}$ and $\Delta H_c^\ominus[C_2H_6(g)] = -1560\ \text{kJ mol}^{-1}$.

Carbon exists as the allotropes graphite and diamond. Graphite is the standard state of carbon at $298\ \text{K}$ and $100\ \text{kPa}$.

The standard enthalpy change for $C(s,\text{ graphite}) \to C(s,\text{ diamond})$ is $+1.9\ \text{kJ mol}^{-1}$.