Chapter 5, Problem 81
Without doing any calculations, predict the sign of H for each of the following reactions: (a) NaCl1s2¡Na+ 1g2 + Cl-1g2
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Methanol (CH3OH) is used as a fuel in race cars. (b) Calculate the standard enthalpy change for the reaction, assuming H2O(g) as a product.
Methanol (CH3OH) is used as a fuel in race cars. (c) Calculate the heat produced by combustion per liter of methanol. Methanol has a density of 0.791 g/mL.
Methanol (CH3OH) is used as a fuel in race cars. (d) Calculate the mass of CO2 produced per kJ of heat emitted.
Use bond enthalpies in Table 5.4 to estimate H for each of the following reactions: (a)
(a) The nitrogen atoms in an N2 molecule are held together by a triple bond; use enthalpies of formation in Appendix C to estimate the enthalpy of this bond, D(N‚N). (b) Consider the reaction between hydrazine and hydrogen to produce ammonia, N2H41g2 + H21g2¡2 NH31g2. Use enthalpies of formation and bond enthalpies to estimate the enthalpy of the nitrogen– nitrogen bond in N2H4. (c) Based on your answers to parts (a) and (b), would you predict that the nitrogen–nitrogen bond in hydrazine is weaker than, similar to, or stronger than the bond in N2 ?
Consider the reaction 2 H2(g) + O2(g) → 2 H2O(l). (a) Use the bond enthalpies in Table 5.4 to estimate H for this reaction, ignoring the fact that water is in the liquid state.