Concept explainers
A common misconception is that the following
instead of
- a What evidence do you have that the second reaction is correct?
- b How would the enthalpy of the wrong reaction compare with that of the correct reaction?
- c How could you calculate the enthalpy change for the wrong reaction (Chapter 6)?
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OWLv2 with Student Solutions Manual eBook for Ebbing/Gammon's General Chemistry, 11th Edition, [Instant Access], 4 terms (24 months)
- Compounds with carboncarbon double bonds, such as ethylene, C2H4, add hydrogen in a reaction called hydrogenation. C2H4(g)+H2(g)C2H6(g) Calculate the enthalpy change for this reaction, using the following combustion data: C2H4(g)+3O2(g)2CO2(g)+2H2O(l);H=1411kJC2H6(g)+72O2(g)2CO2(g)+3H2O(l);H=1560kJH2(g)+12O2(g)H2O(l);H=286kJarrow_forwardHydrazine, N2H4, is a colorless liquid used as a rocket fuel. What is the enthalpy change for the process in which hydrazine is formed from its elements? N2(g)+2H2(g)N2H4(l) Use the following reactions and enthalpy changes: N2H4(l)+O2(g)N2(g)+2H2O(l);H=622.2kJH2(g)+12O2(g)H2O(l);H=285.8kJarrow_forwardWhich of the enthalpies of combustion in Table 5.2 the table are also standard enthalpies of formation?arrow_forward
- A 0.470-g sample of magnesium reacts with 200 g dilute HCl in a coffee-cup calorimeter to form MgCl2(aq) and H2(g). The temperature increases by 10.9 C as the magnesium reacts. Assume that the mixture has the same specific heat as water and a mass of 200 g. (a) Calculate the enthalpy change for the reaction. Is the process exothermic or endothermic? (b) Write the chemical equation and evaluate H.arrow_forwardWith a platinum catalyst, ammonia will burn in oxygen to give nitric oxide, NO. 4NH3(g)+5O2(g)4NO(g)+6H2O(g);H=906kJ What is the enthalpy change for the following reaction? NO(g)+32H2O(g)NH3(g)+34O2(g)arrow_forwardEnthalpy changes for the following reactions can be determined experimentally: N2(g) + 3 H2(g) 2 NH3(g) rH = 91.8 kJ/mol-rxn 4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g) rH = 906.2 kJ/mol-rxn H2(g) + O2(g) H2O(g) rH = 241.8 kl/mol-rxn Use these values to determine the enthalpy change for the formation of NO(g) from the elements (an enthalpy change that cannot be measured directly because the reaction is reactant-favored). N2(g) + O2(g) NO(g) rH = ?arrow_forward
- Chloromethane, CH3Cl, a compound found throughout the environment, is formed in the reaction of chlorine atoms with methane. CH4(g) + 2 Cl(g) CH3Cl(g) + HCl(g) (a) Calculate the enthalpy change for the reaction of CH4(g) and CI atoms to give CH3CI(g) and HCl(g). Is the reaction exo- or endothermic? (b) Draw an energy level diagram that shows how the various enthalpies in this problem are related.arrow_forwardUse 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)arrow_forwardIs the following reaction the appropriate one to use in determining the enthalpy of formation of methane, CH4(g)? Why or why not? C(g)+4H(g)CH4(g)arrow_forward
- The Romans used calcium oxide, CaO, to produce a strong mortar to build stone structures. Calcium oxide was mixed with water to give Ca(OH)2, which reacted slowly with CO2 in the air to give CaCO3. Ca(OH)2(s) + CO2(g) CaCO3(s) + H2O(g) (a) Calculate the standard enthalpy change for this reaction. (b) How much energy is evolved or absorbed as heat if 1.00 kg of Ca(OH)2 reacts with a stoichiometric amount of CO2?arrow_forwardUse standard enthalpies of formation in Appendix L to calculate enthalpy changes for the following: (a) 0.054 g of sulfur burns, forming SO2(g) (b) 0.20 mol of HgO(s) decomposes to Hg() and O2(g) (c) 2.40 g of NH3(g) is formed from N2(g) and excess H2(g) (d) 1.05 102 mol of carbon is oxidized to CO2(g)arrow_forwardThe enthalpy change for the reaction of hydrogen gas with fluorine gas (o produce hydrogen fluoride is 542 U for the equation as written: mg src=Images/HTML_99425-10-41QAP_image001.jpg alt="" align="top"/> l type='a'> What is the enthalpy change per mole of hydrogen fluoride produced? Is the reaction exothermic or endothermic as written? What would be the enthalpy change for the reverse of the given equation (that 1%, for the decomposition of HF into its constituent elements)?arrow_forward
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