Calculate the change in entropy as the 2.00 lbs of liquid butane (CH3CH2CH2CH3)

Question

Calculate the change in entropy as the 2.00  lbs of liquid butane (CH3CH2CH2CH3) inside a camping stove fuel tank is turned into gaseous butane at a constant temperature of 5.00 C on a brisk morning in the wilderness. For butane, the delta-H of fusion is 8.00 kJ/mol and the delta-H of vaporization is 24.0 kJ/mol. The units are J/K.

What is the change in entropy (S) when you burn a 12.2 g block of sulfur in air to form gaseous sulfur dioxide? The standard entropies data can be found in an Appendix of your text book. The units are J/K.

Thank you

Explanation / Answer

a) 2lb of butane = 907.18g = 907g/ 58.12g/mol = 15.6mol

    delH per mole = 24kJ

     15.6 mole = 15.6mole X 24kJ/mole = 374.7 kJ

      delS = (delH)/T in K = 374.7 / 278.15 K = 1.346kJ/K = 1346 J/K

b) S = 11.62 J/(mol K) for orthorombic sulphur

    S of 12.2 g = 12.2g / 32.0g/mol = 0.38125 mol

    total S = 0.3812 mol X 11.62 J/(mol K) = 4.43 J/ K

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