A.) How much heat energy is required to convert 34.7 g of solid ethanol at -114.

Question

A.) How much heat energy is required to convert 34.7 g of solid ethanol at -114.5 °C to gasesous ethanol at 149.9 °C? The molar heat of fusion of ethanol is 4.60 kJ/mol and its molar heat of vaporization is 38.56 kJ/mol. Ethanol has a normal melting point of -114.5 °C and a normal boiling point of 78.4 °C. The specific heat capacity of liquid ethanol is 2.45 J/g·°C and that of gaseous ethanol is 1.43 J/g·°C.

B.) How much heat energy is required to convert 90.0 g of liquid sulfur dioxide, SO2, at 202.5 K to gaseous SO2 at 263.1 K if the molar heat of vaporization of SO2 is 24.9 kJ/mol, and the specific heat capacity (C) of liquid SO2 is 1.36 J/(g ·°C)?

Explanation / Answer

A)

q1 = delta H fus * mass

      = 4.60 kJ per mol * (34.7 g / 46.060844 g per mol)

      = 3.46 kJ

Now lets calculate the amount of energy needed to convert liquid ethanol from -114.5 C to 78.4 C

Change in temperature = 78.4 – (-114.5) = 192.9 C

q2=m*c*delta T

lets put the values in the formula

q2= 34.7 g * 2.45 J per g C * 192.9 C

     = 16399.39 J

16399.39 J* 1 kJ / 1000 J = 16.399 kJ

Now we calculate the energy needed to evaporate the ethanol at its boiling point

q3= delta H vap * m

q3= 38.56 kJ per mol * (34.7 g / 46.060844 gepr mol)

      = 29.05 kJ

Now we calculate the energy needed to raise the temperature of the gases ethanol from 78.4 C to 149.9 C

Change in the temperature T2-T1 = 149.9 C – 78.4 C =71.5 C

q4 = m*c*delta T

q4= 34.7 g * 1.43 J per g C *71.5 C

q4 = 3547.90 J

3547.90 J * 1 kJ/ 1000 J = 3.55 kJ

Now lets calculate the total energy needed

Q total = q1 +q2 +q3+q4

Q total = 3.46 kJ+16.399 kJ+29.05 kJ+3.55 kJ

Q total = 52.46 kJ

Hence total amount of energy needed for the conversion is = 52.46 kJ

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.