The heat of fusion ΔHf, of butane (C4H10) is 4.7 kl/mol. Calculate the change in entropy ΔS when 202. g of butane freezes at -138.0 C. Be sure your answer contains a unit symbol. Round your answer to 2 significant digits

Respuesta :

Answer:

-1.2 × 10² J/K

Explanation:

The molar mass of butane is 58.12 g/mol. The moles corresponding to 202 g are:

202 g × (1 mol/58.12 g) = 3.48 mol

The heat of fusion of butane is 4.7 kJ/mol. The heat (Q) associated with the freezing of 3.48 moles of butane is:

Q = -ΔHf × n

Q = -4.7 kJ/mol × 3.48 mol

Q = -16 kJ

The freezing point is -138.0°C + 273.15 = 135.2 K. The change in entropy when 3.48 moles of butane freeze at 135.2 K is:

ΔS = Q/T

ΔS = -16 × 10³ J/135.2 K

ΔS = -1.2 × 10² J/K

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