122. One Method of Producing H2 on a Large Scale Is This Chemical Cycle

Ch 6

116. Given the following information and the data in Table 6.2, calculate the molar enthalpy of information for liquid hydrazine, N2H4

N2H4(l) + O2(g)→ N2(g) + H2O(g) △H0 = -543kJ

117. The combination of coke and steam produces a mixture called coal gas, which can be used as a fuel or as a starting material for other reaction. If we assume coke can be represented by graphite, the equation for the production of coal gas is

2C (s) + 2H2O(g) →CH4(g) + CO2(g)

Determine the standard enthalpy change for this reaction from the following standard enthalpies of reaction :

C(s) + H2O(g) →CO(g) + H2(g) △H0 = 131.3kJ

CO(g) + H2O (g)→CO2 (g) + H2(g) △H0 = -41.2kJ

CH4(g) + H2O(g)→ 3H2(g) + CO(g) △H0 = 206.1kJ

122. One method of producing h2 on a large scale is this chemical cycle.

Step1. SO2(g) + H2O(g) + Br (g)→H2SO4 (l) + 2HBr (g)

Step2. H2SO4 (l)→H2O (g) + SO2 (g) + 1/2 O2(g)

Step3. 2HBr (g)→H2 (g) + Br2 (g)

Using the Table of standard enthalpies of formation in Appendix J, calculate △H0 for the overall process, and what is its enthalpy change? Is the overall process exothermic or endothermic ?

135. Suppose that 28.89g ClF3(g) is reacted with 57.3g Na(s) to form NaCl(s) and NaF(s). The reaction occurs at 1bar and 25.0℃Calculate the quantity of energy transferred between the system and surroundings and describe in which direction the energy is transferred.

138. For the four substances in the preceding question, calculate the energy density. Assume that substances that are gases at room temperature have been force to condense to liquids by applying pressure and, if necessary, by lowering temperature. Obtain needed density information from the CRC Handbook of Chemistry and Physics, 80th ed. (Boca Raton, FL: CRC press; 2000)

144. Use an Internet search engine (such as Google) to search for information about storage of hydrogen in single walled carbon nanotubes. Based on what you find, decide whether to purchase stockin a new company that is proposing to commercialize carbon nanotubes as a hydrogen storage medium.