Problem: A sample of a hydrocarbon is combusted completely in O2(g) to produce 24.01 g CO2(g), 4.917 g H2O(g), and 342 kJ of heat.Do you think that the hydrocarbon is one of those listed in Appendix C? Explain your answer.

FREE Expert Solution

Determine the empirical formula of the hydrocarbon: (C and H only)

Recall that:

  • 1 mole of C in 1 mole of CO2
  • 2 moles of H in 1 mole of H2O.


Find moles of C and H:


moles of C=24.01 g CO2×1 mol CO244.01 g CO2×1 mol C1 mol CO2 

moles C = 0.55 mol C


moles of H=4.917 g H2O×1 mol H2O18.02 g H2O×2 mol H1 mol H2O

moles H = 0.545 mol H


Get smallest ratio of C, H (divide by 0.545):


C:0.55 mol C0.545=1           H:0.545 mol H0.545=1     

   


The empirical formula: CH


Balanced equation: 2CH + O2 → CO2 + H2O


Hrxn=H°f,products-H°f,reactants-342 kJ=[24.01 g CO2×1 mol CO244.01 g CO2(-393.5 kJmol)+4.917 g H2O×1 mol H2O18.02 g H2O(-241.8 kJmol)]-[H°f,CH+0]

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Problem Details

A sample of a hydrocarbon is combusted completely in O2(g) to produce 24.01 g CO2(g), 4.917 g H2O(g), and 342 kJ of heat.

Do you think that the hydrocarbon is one of those listed in Appendix C? Explain your answer.

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