Ways to Calculate Enthalpy of Reactions

Determine the standard molar enthalpy of formation of solid Al2O3 from the following equations.

Al (s) + 3 H2O (l) → Al(OH)3 (s) + 3/2 H2 (g) $\Delta H\ =+100\ \frac{kJ}{mol}$

H2 (g) + 1/2 O2 (g) → H2O (l)$\Delta H=-300\ \frac{kJ}{mol}$

The standard enthalpy of fusion for water, ΔHofusion = 6.01 kJ/mol. Calculate the energy required (in kJ) to convert 26.0 g of ice at 0oC to liquid water at 20oC.

Find the standard molar enthalpy of combustion of C2H5OH using the standard enthalpy of formations below.

$\Delta H_f(C_2H_5OH_{(l)}) = -277.7\ kJ/mol$

$\Delta H_f(CO_{2(g)}) = -393.5\ kJ/mol$

Using the table below, answer the following questions about the hydrogenation reactions of acetylene:

a) Calculate the enthalpy of formation of ethylene, C2H4, considering ΔHrxn = -174.4kJ/mol

$C_2H_2+H_2\to C_2H_4$

Calculate the enthalpy for the following reaction.

2 C2H6 (g) + 7 O=O (g) → 4 O=C=O (g) + 6 H-O-H (g)

The following are bond dissociation energies (kJ/mol):

The reaction of

$H_{2(g)}+CO_{2(g)}\leftrightarrow H_2O_{(g)}+CO_{(g)}\ at\ 2000K\ K_P=4.40$

Calculate ΔG for this reaction

Calculate ΔHof of SO2(g) given the following: (answer in kJ)

$S_{(s)}+1.5O_{2(g)}\to SO_{3(g)}, \Delta H=-395.8kJ$

$$$2SO_{2(g)}+O_{2(g)}\to 2SO_{3(g)}, \Delta H=-198.2kJ$

Find ΔHo for the following reaction if 12.0 g of N2H4 is consumed in excess N204.

$2N_2H_{4(l)}+N_2O_{4(g)}\to 3N_{2(g)}+4H_2O_{(l)}$

The following enthalpies of formation are provided:

What is the enthalpy of the following reaction when 0.35 g of Mg2+ is produced? Use the following information:

ΔH°f[Mg(OH)2(s)] = −924.5 kJ

ΔH°f[NH4+(aq)] = −132.5 kJ

Ethene gas (C2H4) reacts with fluorine gas according to the following balanced equation:

$C_2H_4 (g) + 6 F_2 (g) → 2 CF_4 (g) + 4 HF (g) \qquadΔ_rH° = −3012\ kJ/mol·rxn\ @ \ 25°C$

$\def\arraystretch{1.5} \begin{array}{|c|c|} \hline \rm{Substance} & △_fH° \ @ \ 25°C(kJ/mol) \\ \hline C_2H_4 (g) & ?? \\ \hline F_2 (g) & 0 \\ \hline CF_4 (g) & – 933 \\ \hline HF (g) & – 273.3 \\ \hline \end{array}$

Consider the following balanced chemical equation:

$2 CℓF_3(g) + 2 O_2(g) → Cℓ_2O (g) + 3 F_2O (g) \qquad ∆_rH° = ???$

$\def\arraystretch{1.5} \begin{array}{|c|c|} \hline \rm Substance & △_fH° \ @ \ 25°C \ (kJ/mol) \\ \hline CℓF_3 (g) & ?? \\ \hline Cℓ_2O (g) & 80.3 \\ \hline F_2O (g) & – 21.7 \\ \hline F_2 (g) & 0 \\ \hline \end{array}$

Consider the following balanced chemical reaction and the bond dissociation energies for the partial combustion of hydrogen sulfide:

What is the enthalpy change ΔrH for this reaction?

Estimate the heat of reaction at 298 K for the reaction shown, given the average bond energies below.

$Br_2 (g)+3F_2 (g)→2BrF_3 (g)$

$\def\arraystretch{1.5} \begin{array}{c} \rm Bond &&&& \rm Bond \ Energy \\ \hline Br-Br &&&& 193 kJ/mol\\ F-F &&&& 155 kJ/mol\\ Br-F &&&& 249 kJ/mol\\ \end{array}$

Given the following at 25°C and 1.00 atm:

$$ $\def\arraystretch{1.5}\begin{array}{cc}\rm Reaction&\Delta H\degree\\\cfrac{1}{2} N_2 (g)+O_2 (g)→NO_2 (g)&33.2 kJ \\N_2 (g)+2O_2 (g)→N_2 O_4 (g)&11.1 kJ\end{array}$$$

The total bond enthalpy for F2 is 156.9 kJ/mol and the total bond enthalpy of I2 is 152.5 kJ/mol. Using the thermochemical equation below, what is the total bond enthalpy of IF7?

Liquification of fuels is an important process that allows fuel to be transported more safely and more easily around the world. Oxidizing methane transforms it from a gas to a liquid, methanol, which is much easier to transport. Using the data provided calculate $\Delta H$for the oxidation of methane (CH4) shown below

$\begin{array}{c} CH_{4(g)}\ +\ 1/2\ O_{2(g)} \rightarrow CH_3OH_{(l)} \\ \\ \Delta H^o_f(CH_{4(g)})=-74.9 kJ\ mol^{-1} \\ \Delta H_f^o(CH_3OH_{(l)}=-238.6\ kJ\ mol^{-1} \end{array}$

Calculate the ΔH for the reaction below IF5 (g) → IF3 (g) + F2 (g)

IF (g) + F2 (g) → IF3 (g) ΔH = -390 kJ IF (g) + 2 F2 (g) → IF5 (g) ΔH = -745 kJ

The standard enthalpy of formation of ethanol ${\small \left(\text{C}_2\text{H}_5\text{OH}\right)}$ is -277.7 kJ/mol. Write the chemical equation to which this value applies.

Solution:

The standard enthalpy of formation for $NO_2\left(g\right)$ is 33.18 kJ/mol, and the standard enthalpy of partial combustion of nitrogen to NO(g) is 90.25 kJ/mol. Calculate the standard enthalpy of combustion of NO(g) to NO2(g).

Calculate $\Delta H\degree$ for the reaction below, which requires catalytic acid to proceed

$C_6H_{12}\left(l\right)+H_2O\left(l\right)\to C_6H_{13}OH\left(l\right)$

Given:

Consider the following reaction:

$N_2H_4(I)+O_2\rightarrow N_2(g)+2\ H_2O(I)\quad \Delta H=-622.2\ kJ$

Given the following data, calculate the heat of reaction for the same reaction where water is a gaseous product instead of a liquid:

1. A 56.0 g block of iron heated to 90 °C is placed in a 4.8 kg water bath at 20 °C. What will be the final temperature of the iron? heat capacity of iron c = 0.450 J /gK, heat capacity of water is 4.185 J/gK

The following reaction enthalpies are provided:

$H_{2(g)}+\frac{1}{2}O_{2(g)}\to H_2O_{(l)},\Delta H_1=-285.8kJ/mol\hspace{70pt} (1)$

$C_{(s)}+O_{2(g)}\to CO_{2(g)},\Delta H_2=-293.5kJ/mol \hspace{80pt} (2)$