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Enthalpy of Formation

Related Topics

Wize University Chemistry Textbook > Thermodynamics: Part 1: (0th law, 1st law, Calorimetry, Enthalpy)

Hess' Law Method

3 Activities

Wize University Chemistry Textbook > Thermodynamics: Part 1: (0th law, 1st law, Calorimetry, Enthalpy)

Heats of Formation Method

4 Activities

Calculate ΔHf\Delta H_f of SO2SO_2
S+1.5O2→SO3ΔH=−395.8kJ2SO2+O2→2SO3ΔH=−198.2kJ\begin{array}{}S+1.5 O_2\rightarrow SO_3\quad \Delta H=-395.8 kJ\\2SO_2+O_2\rightarrow 2SO_3\quad \Delta H=-198.2kJ\end{array}



More Hess' Law Method Questions:
Practice: Calculating the Enthalpy of a Reaction Using Hess' Law
What is the ΔHrxn for the following reaction?
2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g)
Hess' Law: Enthalpy of reaction
Given that the ΔfH0\Delta_fH^0 of ozone O3(g){\rm O}_{3(g)} is 142.67 kJ mol−1142.67\ kJ\ mol^{-1} and the reaction shown below, calculate the enthalpy for the unknown reaction
3/2 O2+I(aq)−→IO3(aq)−ΔH0=−202 kJ mol−1IO3(aq)−→I(aq)−+O3(g)ΔH0=???\begin{array}{ll} \rm 3/2\ O_2\quad+\quad I_{(aq)}^-\quad\overrightarrow{\hspace{1.5cm}}\quad IO_{3(aq)}^- &\hspace{1.5cm} \Delta H^0=-202\ kJ\ mol^{-1}\\[10pt] \rm IO_{3(aq)}^-\quad \overrightarrow{\hspace{1.5cm}}\quad I_{(aq)}^-\quad +\quad O_{3(g)} &\hspace{1.5cm} \Delta H^0=??? \end{array}
Practice: Calculating the Enthalpy of a Reaction Using Hess' Law
What is the ΔHrxn for the following reaction?
2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g)
Practice: Calculating the Enthalpy of a Reaction Using Hess' Law
What is the ΔHrxn for the following reaction?
2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g)
Hess' Law: Enthalpy of reaction
What is the ΔHrxn for the following reaction?
2C2H6(g) + 7O2(g) --> 4CO2(g) + 6H2O(g)
1) 2C + 3H2 --> C2H6 ΔH=-84.68kJ
Hess' Law: Enthalpy of reaction
Given that the ΔfH0\Delta_fH^0 of ozone O3(g){\rm O}_{3(g)} is 142.67 kJ mol−1142.67\ kJ\ mol^{-1} and the reaction shown below, calculate the enthalpy for the unknown reaction
3/2 O2+I(aq)−→IO3(aq)−ΔH0=−202 kJ mol−1IO3(aq)−→I(aq)−+O3(g)ΔH0=???\begin{array}{ll} \rm 3/2\ O_2\quad+\quad I_{(aq)}^-\quad\overrightarrow{\hspace{1.5cm}}\quad IO_{3(aq)}^- &\hspace{1.5cm} \Delta H^0=-202\ kJ\ mol^{-1}\\[10pt] \rm IO_{3(aq)}^-\quad \overrightarrow{\hspace{1.5cm}}\quad I_{(aq)}^-\quad +\quad O_{3(g)} &\hspace{1.5cm} \Delta H^0=??? \end{array}
Enthalpy of Formation
Chlorine trifluoride is an interhalogen compound that reacts, usually explosively, with almost every known substance on earth, even relatively inert compounds, including glass, sand, concrete, and asbestos--which is a notorious flame-retardant material. It is a stronger oxidizing agent than O2, and is usually stored in metal canisters that are coated with F2 gas. Do not try to put out a fire caused by a ClF3 spill using water, because that will result in an explosive reaction that produces HF, a deadly gas. Trials involving ClF3 as war weapons were done during WWII, but handling, storing, and transporting this compound was more trouble than it was worth. Evil scientists need to determine the enthalpy of formation of ClF3, represented by this equation:
ClF(g)+ F2(g) → ClF3(g)       ΔH=?ClF_{\left(g\right)}+\ F_{2\left(g\right)}\ \rightarrow\ ClF_{3\left(g\right)}\ \ \ \ \ \ \ \Delta H=?
However, they were only able to determine the enthalpies of the following reactions:
Hess' Law: Enthalpy of formation
Given that the ΔfH0\Delta_fH^0 of ozone O3(g){\rm O}_{3(g)} is 142.67 kJ mol−1142.67\ kJ\ mol^{-1} and the reaction shown below, calculate the enthalpy for the unknown reaction
3/2 O2+I(aq)−→IO3(aq)−ΔH0=−202 kJ mol−1IO3(aq)−→I(aq)−+O3(g)ΔH0=???\begin{array}{ll} \rm 3/2\ O_2\quad+\quad I_{(aq)}^-\quad\overrightarrow{\hspace{1.5cm}}\quad IO_{3(aq)}^- &\hspace{1.5cm} \Delta H^0=-202\ kJ\ mol^{-1}\\[10pt] \rm IO_{3(aq)}^-\quad \overrightarrow{\hspace{1.5cm}}\quad I_{(aq)}^-\quad +\quad O_{3(g)} &\hspace{1.5cm} \Delta H^0=??? \end{array}
Calculate the heat of formation for Ethyne (C2H2) using the thermochemical information below.
2 C(s)+H2(g)→ C2H2(g)         ΔH0 = ???2\ C_{\left(s\right)}+H_{2\left(g\right)}\rightarrow\ C_2H_{2\left(g\right)}\ \ \ \ \ \ \ \ \ \Delta H^0\ =\ ???
C2H2+5/2O2→2 CO2+H2OΔH0=−1299.5kJC+O2→CO2−393.5kJH2+1/2O2→H2O−285.8kJ\begin{array}{lr} C_2H_2 + 5/2 O_2 \rightarrow 2\ CO_2 + H_2O & \Delta H^0 = -1299.5 kJ \\ C + O_2 \rightarrow CO_2 & -393.5 kJ \\ H_2 + 1/2 O_2 \rightarrow H_2O & -285.8 kJ \\ \end{array}
Thermochemistry: Enthalpy of formation
Calculate ΔHof of SO2(g) given the following:
S(s)+1.5O2(g)→SO3(g),ΔH=−395.8kJS_{(s)}+1.5O_{2(g)}\to SO_{3(g)}, \Delta H=-395.8kJ
2SO2(g)+O2(g)→2SO3(g),ΔH=−198.2kJ2SO_{2(g)}+O_{2(g)}\to 2SO_{3(g)}, \Delta H=-198.2kJ
Hess' Law: Enthalpy of reaction
Given that the ΔfH0\Delta_fH^0 of ozone O3(g){\rm O}_{3(g)} is 142.67 kJ mol−1142.67\ kJ\ mol^{-1} and the reaction shown below, calculate the enthalpy for the unknown reaction
3/2 O2+I(aq)−→IO3(aq)−ΔH0=−202 kJ mol−1IO3(aq)−→I(aq)−+O3(g)ΔH0=???\begin{array}{ll} \rm 3/2\ O_2\quad+\quad I_{(aq)}^-\quad\overrightarrow{\hspace{1.5cm}}\quad IO_{3(aq)}^- &\hspace{1.5cm} \Delta H^0=-202\ kJ\ mol^{-1}\\[10pt] \rm IO_{3(aq)}^-\quad \overrightarrow{\hspace{1.5cm}}\quad I_{(aq)}^-\quad +\quad O_{3(g)} &\hspace{1.5cm} \Delta H^0=??? \end{array}
Practice: Calculating the Enthalpy of a Reaction Using Hess' Law
What is the ΔHrxn for the following reaction?
2C2H6(g) + 7O2(g) --> 4CO2(g) + 6H2O(g)
More Heats of Formation Method Questions:
Find the standard molar enthalpy of combustion of C2H5OH using the standard enthalpy of formations below.
ΔHf(C2H5OH(l))=−277.7 kJ/mol\Delta H_f(C_2H_5OH_{(l)}) = -277.7\ kJ/mol
ΔHf(CO2(g))=−393.5 kJ/mol\Delta H_f(CO_{2(g)}) = -393.5\ kJ/mol
The standard enthalpy of formation for the amino acid glycine C2H5NO2(s) is –528 kJ/mol at 25°C. Which reaction below has an enthalpy change equal to this value?
Which of the following represents a proper formation reaction for the product indicated? (select all that apply)
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 ΔH\Delta Hfor the oxidation of methane (CH4) shown below
CH4(g) + 1/2 O2(g)→CH3OH(l)ΔHfo(CH4(g))=−74.9kJ mol−1ΔHfo(CH3OH(l)=−238.6 kJ mol−1\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}
Heats of Formation

Heats of Formation
How much heat is required for the following reaction to go given that we start with 37g of CO2(g)?
CO2(g) + 2H2O(l) --> CH4(g) + 2O2(g) ∆H= +890.4kJ/mol
Heats of Formation

Find ΔHo for the following reaction if 12.0 g of N2H4 is consumed in excess N204.
2N2H4(l)+N2O4(g)→3N2(g)+4H2O(l)2N_2H_{4(l)}+N_2O_{4(g)}\to 3N_{2(g)}+4H_2O_{(l)}
The following enthalpies of formation are provided:
Find the ΔH for the atomization of gaseous propane (CH3CH2CH3). The bond enthalpy for C-H bonds is 414 kJ/mol and the bond enthalpy for C-C bonds is 347 kJ/mol.
Please report your answer to four significant figures in kJ/mol. Do NOT include units in the answer field
Enthalpy of Reactions
Practice: Formation Reaction
Write a reaction for the heat of formation for dimethylaminopyridine, (CH3)2NC5H4N.