Ethanol (C₂H₅OH)melts at -114°C.The enthalpy of fusion is 5.02 kJ/mol.The specific heats of solid and liquid ethanol are 0.97 J/g∙K and 2.3 J/g∙K,respectively.How much heat (kJ)is needed to convert 25.0 g of solid ethanol at -135°C to liquid ethanol at -50°C? A)207.3 kJ B)-12.7 kJ C)6.91 kJ D)4192 kJ E)9.21 kJ

Question

Quizplus · Accepted Answer

To find the total heat required, calculate the heat for each step: heating the solid to its melting point, melting the solid, and heating the liquid. 1) Heat solid ethanol from -135°C to -114°C: q = m*c*ΔT = 25.0 g * 0.97 J/g∙K * (21 K) = 509.25 J. 2) Melt the ethanol: q = n*ΔH_fusion = (25.0 g / 46.08 g/mol) * 5.02 kJ/mol = 2.72 kJ. 3) Heat liquid ethanol from -114°C to -50°C: q = m*c*ΔT = 25.0 g * 2.3 J/g∙K * (64 K) = 3680 J. Convert all to kJ and sum: 0.509 kJ + 2.72 kJ + 3.68 kJ = 6.91 kJ.

Ethanol (C2H5OH)melts at -114°C

Ethanol (C₂H₅OH)melts at -114°C