Answer:
31.0kJ
Step-by-step explanation:
To a temperature of 19.8°C
To solve this question we must, as first, find the heat necessary to melt the 78.0g of methanol. Then, the heat to increase the temperature from the melting point (-97.53°C) to 19.8°C as follows:
Melting methanol -Molar mass: 32.04g/mol-
78.0g * (1mol / 32.04g) = 2.434 moles
As heat of fusion is 3.215kJ/mol:
2.434 moles * (3.215kJ / mol) = 7.83kJ
Heating methanol:
Q = S*m*ΔT
Where Q is heat in J,
S is specific heat = 2.53J/g°C
m is mass of methanol = 78.0g
ΔT is change in temperature = (19.8°C - (-97.53°C)) = 117.33°C
Replacing:
Q = 2.53J/g°C*78.0g*117.33°C
Q = 23154J
Q = 23.2kJ
Total heat is:
31.0kJ