In an experiment using a simple tin calorimeter 18.95g of methanol was burned to raise the temperature of 708g of water by 29.5 degrees celsius. Using this evidence, calculate the molar enthalpy of combustion of methanol (to produce water as a vapor).

Answer 1

To calculate the molar enthalpy of combustion of methanol, we need to use the following equation:

q = m * c * ΔT

where:
q = heat transferred in Joules
m = mass of the substance (water) in grams
c = specific heat capacity of the substance (water) in J/g °C
ΔT = change in temperature in °C

First, let's calculate the heat transferred to the water using the given information:

q = 708g * 4.18 J/g °C * 29.5 °C
q = 69953.8 J

Next, we need to convert the mass of methanol burned (18.95g) to moles of methanol. The molar mass of methanol (CH3OH) is 32.04 g/mol.

moles of methanol = 18.95g / 32.04 g/mol
moles of methanol = 0.59 mol

Now, we can calculate the molar enthalpy of combustion using the equation:

ΔH = q / moles of methanol

ΔH = 69953.8 J / 0.59 mol
ΔH = 118559.0 J/mol

Thus, the molar enthalpy of combustion of methanol (to produce water as a vapor) is approximately 118559 J/mol.