Calculate the amount of heat needed to melt 78.0g of solid methanol (CH^3OH) and bring it to a temperature of . Round your answer to 3 significant digits. Also, be sure your answer contains a unit symbol.

31.0kJ

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: