Calculate the standard enthalpy?

CH3OH (l) + 1.5O2 (g) > CO2 (g) + 2H2O (g)

Calculate the standard enthalpy change for the reaction, assuming H2O (g) as a product.

Calculate the heat produced by combustion per liter of methanol. Methanol has a density of 0.791 g/mL.

Calculate the mass of CO2 produced per kJ of heat emitted.

1 Answer

  • Calculate the standard enthalpy change for the reaction, assuming H2O (g) as a product.

    ***Just use the standard heat of reactions for each substance in the balanced equation (found in appendix C if you're using Chemistry The Natural Science), and use Hess's Law (deltaH=sum of (number of moles)(deltaH of products) - sum of (number of moles)(deltaH of reactants).

    [-393.5 + 2(-241.82)] - [-238.6 + (3/2)(0)]

    = -638.54 (four sig figs = -638.5)

    Calculate the heat produced by combustion per liter of methanol. Methanol has a density of 0.791 g/mL.

    ***Follow the units to find your answer... you want to go from g/mL to kJ/L

    .791 g/mL (10^3mL/1L)(1mol methanol/32.04g)(-638.5kJ/1mol methanol)=1.58x10^4

    Calculate the mass of CO2 produced per kJ of heat emitted.

    ***Again just use what you have and follow your units. 1 mol of CO2 is used for every 1 mol of methanol. The molar mass of CO2 is 40.010g. You divide that by the enthalpy of reaction (in kJ). This way you will end up with g/kJ.

    40.010g/638.5kJ(negative sign isn't used here) = 6.892x10^-2

    Source(s): chem student, use mastering chemistry

Leave a Reply

Your email address will not be published. Required fields are marked *

Related Posts