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I went through these two problems the simplest way I could find,using the formula:

ΔH°f298 = ΣνiΔH°i

1. In order to determine the ΔH°f298 for urea, Peter decides tocarry out a calorimetric analysis. He determines that the heat ofcombustion of urea, (NH2)2CO(s), at 25°C is 589,000 J mol-1 whenthe products are CO2(g), H2O(l), and N2(g). Calculate ΔH°f298 forurea at this value?It is later found that the previous analysis hadsome errors and that the heat of combustion of urea is actually603,200 J mol-1. By how much does the ΔH°f298 change?

2. What are the standard heats of combustion of methane andpropane gas at 25°C if the combustion products are H2O(l) andCO2(g)?

For problem 1.) I got -963000J/mol for the heat of formationoriginally, and -991000J/mol.

2.) I got -891000J/mol for methane, and -2220000J/mol.

How far am I off and how do I fix this?

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Hubert Koch
Hubert KochLv2
28 Sep 2019

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Related questions

DearChegg Lifesaver. Here are the requirements:

1.Use given values as stated in questions below.

2.Clearly State Answer

3.(Please) LEAVE A COMMENT if you are currently working on anyproblems.

4.Formany of these problems you will need to use tabulated thermodynamicdata. Use the Information provided after problem 17.



---------------------------------------Questions---------------------------------------------------



1.Write a balanced formation equation for HNO3 at standardconditions. For the answer, enter the sum all of the coefficientsin the balanced equation. (If thisis not an integer, enter it as a decimal, not a fraction.)


2.Calculate ?H° for the following reaction:

SiO2(s)+ 4HF(g) ? SiF4(g) + 2H2O(g)


3.Use heat of formation data to determine ?H° for the reaction:

2NH3(g)? N2(g) + 3H2(g)


4.Calculate the mass of methane that must be burned to provide enoughheat to convert 330.0 g of water at 37.0°C into steam at 124.0°C.(Assume that the H2Oproduced in the combustion reaction is steam rather than liquidwater.)


5.Acetylene burns in air according to the following equation:

C2H2(g)+ 5/2 O2(g) ? 2 CO2(g) + H2O(g)

with?H° = -1255.8 kJ.

Giventhat ?Hf° for CO2(g) = -393.5 kJ/mol and ?Hf° for H2O(g) is -241.8kJ/mol, what is ?Hf° for C2H2(g)?






6.Given the following data:

HNO3(l)? 1/2N2(g) + 3/2O2(g) + 1/2H2(g) ?H° = 174.1 kJ

2N2O5(g)? 2N2(g) + 5O2(g) ?H° = -28.4 kJ

H2O(l)? H2(g) + 1/2O2(g) ?H° = 285.8 kJ


Calculate?H° for the reaction:

2HNO3(l)? N2O5(g) + H2O(l)

Notethat you should be able to answer this one without needing to useany additional information from the thermo table.


7.Hydrocarbons containing halogens are very useful molecules insynthetic chemistry. Use tabulated thermodynamic data as needed tocalculate ?Hf° for the reactionproduct in the equation shown below if ?H° for the reaction is-177.66 kJ.

C2H4(g)+ Cl2(g) ? CH2ClCH2Cl(g)



8.Identify the following statements as true or false. (Use thedrop-down menu and select "True" or "False" for each. You must getall 6 correct.)

Allsystems become more disordered spontaneously.

Both?Ssys and ?Ssurr must equal zero at equilibrium.

Theentropy of the universe is constant; the energy of the universedecreases towards a minimum.

Allspontaneous processes release heat.

Ifa reaction is spontaneous, the reverse reaction is non-spontaneous.

Ifa process decreases the randomness of the particles of a system,the entropy of the system increases.


9.Use tabulated thermodynamic data to calculate ?S° for the reaction:

PbO2(s)+ 2Ni(s) ? Pb(s) + 2NiO(s)



10.Calculate ?S° for the combustion of ethane (C2H6) to form carbondioxide and gaseous water.



11.Urea ((NH2)2CO) can be formed from ammonia and carbon dioxide asshown in the following reaction. The ?H° value for this synthesisis -134.0 kJ. Calculatethe ?H°f for urea.

2NH3(g)+ CO2(g) ? (NH2)2CO(s) + H2O(l)


12.The ?S° value for urea the synthesis reaction above is -424.0 J/K.Calculate S° for urea.

Tries0/99


13.Calculate ?G° for the synthesis of urea under standard conditions(298 K and 1 atm).

Tries0/99


14.Compute the standard free energy change for the following reaction.

O3(g)+ NO(g) ? NO2(g) + O2(g)

Tries0/99


15.The most important commercial process for generating hydrogen gasis the water-gas shift reaction:

CH4(g)+ H2O(g) ? CO(g) + 3H2(g)

Usetabulated thermodynamic data to find ?G° for this reaction at thestandard temperature of 25°C.


16.Now calculate ?G°1100 for this process when it occurs at 1100 K.


17.The molar enthalpy of fusion (?H°) of fluorine is 0.260 kJ/mol, andthe molar entropy of fusion (?S°) of fluorine is 4.851 J/mol K.Using this information,estimate the freezing point of fluorine. (You must answer inKelvin.)

1- The molar heat capacity of silver is 25.35 J/mol⋠∘C. How much energy would it take to raise the temperature of 8.20 g of silver by 14.5 ∘C?

Express your answer with the appropriate units.

_____________

Part A

Calculate the enthalpy of the reaction

2NO(g)+O2(g)→2NO2(g)

given the following reactions and enthalpies of formation:

12N2(g)+O2(g)→NO2(g), ΔH∘A=33.2 kJ

12N2(g)+12O2(g)→NO(g), ΔH∘B=90.2 kJ

Express your answer with the appropriate units.

2- A total of 2.00 mol of a compound is allowed to react with water in a foam coffee cup and the reaction produces 196 g of solution. The reaction caused the temperature of the solution to rise from 21.00 to 24.70 ∘C. What is the enthalpy of this reaction? Assume that no heat is lost to the surroundings or to the coffee cup itself and that the specific heat of the solution is the same as that of pure water.

Enter your answer in kilojoules per mole of compound to three significant figures.

_________

3- A volume of 110. mL of H2O is initially at room temperature (22.00 ∘C). A chilled steel rod at 2.00 ∘Cis placed in the water. If the final temperature of the system is 21.00 ∘C , what is the mass of the steel bar?

Use the following values:

specific heat of water = 4.18 J/(g⋠∘C)

specific heat of steel = 0.452 J/(g⋠∘C)

Express your answer to three significant figures and include the appropriate units.

Part B

The specific heat of water is 4.18 J/(g⋠∘C). Calculate the molar heat capacity of water.

Express your answer to three significant figures and include the appropriate units.

______-

4- What is the enthalpy for the following reaction?

overall: N2O4→2NO2

Express your answer numerically in kilojoules per mole.

____________

Part B

Calculate the enthalpy of the reaction

4B(s)+3O2(g)→2B2O3(s)

given the following pertinent information:

B2O3(s)+3H2O(g)→3O2(g)+B2H6(g), ΔH∘A=+2035 kJ

2B(s)+3H2(g)→B2H6(g), ΔH∘B=+36 kJ

H2(g)+12O2(g)→H2O(l), ΔH∘C=−285 kJ

H2O(l)→H2O(g), ΔH∘D=+44 kJ

Express your answer with the appropriate units.

_____________

5- What is the balanced chemical equation for the reaction used to calculate ΔH∘f of MgCO3(s)?

If fractional coefficients are required, enter them as a fraction (i.e. 1/3). Indicate the physical states using the abbreviation (s), (l), or (g) for solid, liquid, or gas, respectively without indicating allotropes. Use (aq) for aqueous solution.

Express your answer as a chemical equation.

__________

6- Part A

Determine the enthalpy for this reaction:

Ca(OH)2(s)+CO2(g)→CaCO3(s)+H2O(l)

Express your answer in kilojoules per mole to one decimal place.

_______

Part B

Consider the reaction

Ca(OH)2(s)→CaO(s)+H2O(l)

with enthalpy of reaction

ΔHrxn∘=65.2kJ/mol

What is the enthalpy of formation of CaO(s)?

Express your answer in kilojoules per mole to one decimal place.

________

7- Part A

Write a balanced chemical equation depicting the formation of one mole of H2O2(g) from its elements in their standard states.

Express your answer as a chemical equation. Identify all of the phases in your answer.

_____

Part B

For H2O2(g), find the value of ΔH∘f. (Use Appendix C)

Express your answer using five significant figures.

_____

PART C: Write a balanced chemical equation depicting the formation of one mole of CaCO3(s) from its elements in their standard states.

Express your answer as a chemical equation. Identify all of the phases in your answer.

_____

Part D

For CaCO3(s), find the value of ΔH∘f. (Use Appendix C)

Express your answer using five significant figures.

_____

Part E

Write a balanced chemical equation depicting the formation of one mole of POCl3(l) from its elements in their standard states.

Express your answer as a chemical equation. Identify all of the phases in your answer.

____

Part F

For POCl3(l), find the value of ΔH∘f. (Use Appendix C)

Express your answer using four significant figures.

_____

Part G

Write a balanced chemical equation depicting the formation of one mole of C2H5OH(l) from its elements in their standard states.

Express your answer as a chemical equation. Identify all of the phases in your answer.

_____

Part H

For C2H5OH(l), find the value of ΔH∘f. (Use Appendix C)

Express your answer using four significant figures.

1.According to the following thermochemical equation, if 31.1 g of NO2 is produced, how much heat is released at constant pressure?how much heat is released at constant pressure?

2NO(g) + O2(g) → 2NO2(g);ΔH° = –114.4 kJ

Select one:

a. 114.4 kJ114.4 kJ

b. 1.183×103kJ

c. 2.365×103kJ

d. 38.7 kJ

e. 1.088×105kJ

2.Calculate   ΔU   of a gas for a process in which the gas absorbs   12 J   of heat and does   20 J   of work by expanding.

Select one:

a. 8 J

b. 32 J

c. -32 J

d. 0, because  ΔU is a state function

e. -8 J

3.If q = +56 kJ for a certain process, that process

Select one:

a. requires a catalyst.

b. is exothermic.

c. occurs rapidly.

d. is endothermic.

e. cannot occur.

4.If q = 18 kJ and w = 15 kJ for a certain process, that process

Select one:

a. requires a catalyst.

b. has an increase in internal energy.

c. occurs slowly.

d. is exothermic.

e. cannot occur.

5.What is the change in internal energy of the system (ΔU) if 10 kJ of heat energy is released by the system and  70 kJ  of work is done on the system for a certain process?

Select one:

a. –60 kJ

b. 80 kJ

c. 10 kJ

d. 60 kJ

e. −80 kJ

6.What is the quantity of heat evolved at constant pressure when   26.3 g   H2O(l)   is formed from the combustion of H2(g) and O2(g)?

2H2(g) + O2(g) → 2H2O(l);ΔH° = –571.6 kJ

Select one:

a. 15033 kJ

b. 15.03 kJ

c. 1.72×104 kJ

d. 417.6 kJ

e. 9.57×102 kJ

7.What quantity, in moles, of hydrogen is consumed when 76.8 kJ of energy is evolved from the combustion of a mixture of H2(g) and O2(g)?

H2(g) + O2(g) →2H2O(l);ΔH° = –571.6 kJ

Select one:

a. 2.368 mol

b. 1.184 mol

c. 0.4223 mol

d. 0.2687 mol

e. 1.368 mol

8. Which of the following is an exothermic process?

Select one:

a. work is done by the system on the surroundings

b. heat energy flows from the system to the surroundings

c. work is done on the system by the surroundings

d. heat energy is absorbed by the system

e. none of the above

9. Which of the following statements is correct?

Select one:

a. Internal energy is not a state function.

b. The value of q is negative when heat flows into a system from the surroundings.

c. The value of q is negative in an endothermic process.

d. Heat flows from a system into the surroundings in an exothermic process.

e. Enthalpy is not a state function.

10.X2and F2react according to the following equation, forming XF. (X is an unknown diatomic element)

X2(g)+ F2(g)→2XF(g);ΔH°=+271 kJ

If X2(g) and F2(g) were mixed in a thermally insulated vessel, the reaction that occurred would be

Select one:

a. endothermic, and the temperature of the reaction system would fall.

b. We could not tell unless the original and final temperatures were given.

c. exothermic, and the temperature of the reaction system would fall.

d. exothermic, and the temperature of the reaction system would rise.

e. endothermic, and the temperature of the reaction system would rise.

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