Calculate the amount of heat needed to boil 126. g of methanol, beginning from a temperature of 24.2 C. Be sure your answer has a unit symbol and the correct number of significant digits.

Answer 1

Hi Zaiad,

For this problem, we have two steps. Step one is to find how much energy we need to raise the temperature from 24.2 C to 64.6 C.

Boiling temperature for methanol is 64.6 C

Our initial temperature here is 24.2 C

Q = mc * delta T

Q = 126g * 2.53 J/g*C * (64.6 C - 24.2 C)

Q = 12,878 J

To boil methanol, we need to use heat of vaporization which is 35.21 kJ/mol

molar mass of methanol is 32.04 g/mol

moles of methanol = 126 g / 32.04 g/mol = 3.933 mol

Q = moles of methanol * heat of vaporization

Q = 3.933 mol * 35.21 kJ/mol

Q = 138.46 kJ

Total heat required will be 12,878 J added to 138.46 kJ, which is 151.338 kJ

This answer rounded to the correct number of significant figures (which is 3) will be 151 kJ

Hope this helps! Have a good day!