Concept explainers
Use standard enthalpies of formation in Appendix L to calculate enthalpy changes for the following:
- (a) 1.0 g of white phosphorus burns, forming P4Ol0(s)
- (b) 0.20 mol of NO(g) decomposes to N2(g) and O2(g)
- (c) 2.40 g of NaCl(s) is formed from Na(s) and excess Cl2(g)
- (d) 250 g of iron is oxidized with oxygen to Fe2O3(s)
(a)
Interpretation:
The enthalpy change for the formation the following reaction has to be determined.
Concept Introduction:
If a reaction proceeds in two or more other reaction,
The change in enthalpy,
Answer to Problem 57PS
The enthalpy change for the formation is
Explanation of Solution
Given mass is
The enthalpy of formation is
The change in enthalpy,
So, the enthalpy change for the formation is
(b)
Interpretation:
The enthalpy change for the formation the following reaction has to be determined.
Concept Introduction:
If a reaction proceeds in two or more other reaction,
Answer to Problem 57PS
The enthalpy change for the formation is
Explanation of Solution
Given mass is
The enthalpy of formation is -
The change in enthalpy,
So, the change in enthalpy is
(c)
Interpretation:
The enthalpy change for the formation the following reaction has to be determined.
Concept Introduction:
If a reaction proceeds in two or more other reaction,
Answer to Problem 57PS
The change in enthalpy is
Explanation of Solution
Given mass is
The enthalpy of formation is
The change in enthalpy,
Energy change =
So, the change in enthalpy is
(d)
Interpretation:
The enthalpy change for the formation the following reaction has to be determined.
Concept Introduction:
If a reaction proceeds in two or more other reaction,
Answer to Problem 57PS
The change in enthalpy is
Explanation of Solution
Given mass is
The enthalpy of formation is
The change in enthalpy,
Energy change =
So, the change in enthalpy is
Want to see more full solutions like this?
Chapter 5 Solutions
Chemistry & Chemical Reactivity
- 9.73 Without looking up any numerical data or doing calculations, predict whether the enthalpy change for each of the following reactions should he positive, negative, or zero. (a) H2O(l)H2O(s) (b) N2(g)2N(g) (c) CH4(g)+2O2(g)CO2(g)+2H2O(l) (d) CO2(s)CO2(g)arrow_forwardWhen 2.50 g of methane burns in oxygen, 125 kJ of heat is produced. What is the enthalpy of combustion per mole of methane under these conditions?arrow_forwardAnother reaction that is used to propel rockets is N2O4(l)+2N2H4(l)3N2(g)+4H2O(g) This reaction has the advantage that neither product is toxic, so no dangerous pollution is released. When the reaction consumes 10.0 g liquid N2O4, it releases 124 kJ of heat. (a) Is the sign of the enthalpy change positive or negative? (b) What is the value of H for the chemical equation if it is understood to be written in molar quantities?arrow_forward
- Give the definition of the standard enthalpy of formation for a substance. Write separate reactions for the formation of NaCl, H2O , C6H12O6, and PbSO4 that have H values equal to Hf for each compound.arrow_forwardCalcium oxide, CaO, is prepared by heating calcium carbonate (from limestone and seashells). CaCO3(s)CaO(s)+CO2(g) Calculate the standard enthalpy of reaction, using enthalpies of formation. The Hf of CaO(s) is 635 kJ/mol. Other values are given in Table 6.2.arrow_forwardThe head of a strike anywhere match contains tetraphosphorus trisulfide, P4S3. In an experiment, a student burned this compound in an excess of oxygen and found that it evolved 3651 kJ of heat per mole of P4S3 at a constant pressure of 1 atm. She wrote the following thermochemical equation: P4S3(s)+8O2(g)P4O10(s)+3SO2(g);H=3651kJ Calculate the standard enthalpy of formation of P4S3, using this students result and the following standard enthalpies of formation: P4O10(s), 3009.9 kJ/mol; SO2(g), 296.8 kJ/mol. How does this value compare with the value given in Appendix C?arrow_forward
- 9.32 The material typically used to heat metal radiators is water. If a boiler generates water at 79.5°C, what mass of water was needed to provide the heat required in the previous problem? Water has a specific heat of 4.184Jg1 C1 .arrow_forwardWhat is the difference between the enthalpy of reaction and the enthalpy of formation? For what chemical reaction(s) are the two quantities the same?arrow_forwardEthylene glycol, HOCH2CH2OH, is used as antifreeze. It is produced from ethylene oxide, C2H4O, by the reaction C2H4O(g)+H2O(l)HOCH2CH2OH(l) Use Hesss law to obtain the enthalpy change for this reaction from the following enthalpy changes: 2C2H4O(g)+5O2(g)4CO2(g)+4H2O(l);H=2612.2kJHOCH2CH2OH(l)+52O2(g)2CO2(g)+3H2O(l);H=1189.8kJarrow_forward
- Ethanol, C2H5OH, is used as a fuel for motor vehicles, particularly in Brazil. (a) Write the balanced equation for the combustion of ethanol to CO2(g) and H2O(g), and, using the data in Appendix G, calculate the enthalpy of combustion of 1 mole of ethanol. (b) The density of ethanol is 0.7893 g/mL. Calculate the enthalpy of combustion of exactly 1 L of ethanol. (c) Assuming that an automobile’s mileage is directly proportional to the heat of combustion of the fuel, calculate how much farther an automobile could be expected to travel on 1 L of gasoline than on 1 L of ethanol. Assume that gasoline has the heat of combustion and the density of n—octane, C8H18(Hf=208.4kJ/mol;density=0.7025g/mL).arrow_forwardA 10.00-g sample of acetic acid, HC2H3O2, was burned in a bomb calorimeter in an excess of oxygen. HC2H3O2(l)+2O2(g)2CO2(g)+2H2O(l) The temperature of the calorimeter rose from 25.00C to 35.84C. If the heat capacity of the calorimeter and its contents is 13.43 kJ/C, what is the enthalpy change for the reaction?arrow_forwardIn the process of isolating iron from its ores, carbon monoxide reacts with iron(III) oxide, as described by the following equation: Fe2O3(s)+3CO(g)2Fe(s)+3CO2(g)H=24.8kJ The enthalpy change for the combustion of carbon monoxide is 2CO(g)+O2(g)2CO2(g)H=566kJ Use this information to calculate the enthalpy change for the equation 4Fe(s)+3O2(g)2Fe2O3(s)H=?arrow_forward
- Chemistry: Principles and PracticeChemistryISBN:9780534420123Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward MercerPublisher:Cengage LearningChemistryChemistryISBN:9781305957404Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCostePublisher:Cengage Learning
- Chemistry: An Atoms First ApproachChemistryISBN:9781305079243Author:Steven S. Zumdahl, Susan A. ZumdahlPublisher:Cengage LearningChemistry for Engineering StudentsChemistryISBN:9781337398909Author:Lawrence S. Brown, Tom HolmePublisher:Cengage LearningChemistry: The Molecular ScienceChemistryISBN:9781285199047Author:John W. Moore, Conrad L. StanitskiPublisher:Cengage Learning