Given the following values for the heats of formation, what is the number of moles of ethane (C2H6, MW 30.0) required to produce 1.00x10^3 kJ of heat by combustion to CO2 (g) and H2O (l). C2H6 (g) + 7/2O2(g) → 2CO2 (g) + 3 H2O (l)

C2H6 (g) ΔHf° = -84.7 kJ/mol
CO2 (g) ΔHf° = -393.5 kJ/mol
H2O (l) ΔHf° = -285.8 kJ/mol

a. 0.595
b. 1.56
c. 0.641
d. can't be determined without ΔHfo for O2
e. 1.68

0.641 moles of ethane

Explanation:

Based on the equation:

C2H6(g) + 7/2O2(g) → 2CO2(g) + 3H2O(l)

We can determine ΔH of reaction using Hess's law. For this equation:

Hess's law: ΔH products - ΔH reactants

ΔH = {2ΔHCO2 + 3ΔHH2O} - {ΔHC2H6}

Pure monoatomic substances have a ΔH = 0kJ/mol; ΔHO2 = 0kJ/mol

ΔH = {2*-393.5kJ/mol + 3*-285.8kJ/mol} - {-84.7kJ/mol}

ΔH = -1559.7kJ/mol

That means when 1 mole of ethane is in combustion there are released 1559.7kJ of heat. To produce 1.00x10³kJ there are needed:

1.00x10³kJ * (1mole ethane / 1559.7kJ) =

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.