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) =

both adhesion and cohesion are attractions.

they are different in that adhesion is the force of attraction between the molecules of two different substances, whereas cohesion is the force of attraction between molecules of the same substance.

possible examples include capillary action, in which the adhesion between water and glass causes the water to rise in a narrow tube against the force of gravity.

because of hydrogen bonding, water is extremely cohesive.

this causes molecules on the surface of water to be drawn inward, which is why drops of water form beads on smooth surfaces.

hope this .