Question

Calculate the deltaH rxn for the production of CO2 and H20 via propane combustion, using thermochemical equations below. Show all work! 3 C (s) + 4 H2 (g) = C3H8 (g) Delta H = (-) 103.9 kJ/mol C (s) + O2 (g) = CO2 (g) Delta H = (-) 393.5 kJ/mol H2 (g) + 1/2 O2 (g) = H2O (g) Delta H = (-)241. 8 kJ/mol Delta H rxn : ?

Answer #1

Calculate ΔH° for the combustion of methane (products are
CO2(g) and H2O(l)), given the following
thermochemical equations:
CH4(g) + O2(g) →CH2O(g) + H2O(g) ΔH = -284 kJ
CH2O(g) + O2(g) →CO2(g) + H2O(g) ΔH = -518 kJ
H2O(g) →H2O(l) ΔH = +44 kJ

Given tha delta hydrogen = -393.5 kJ for the rxn.: C(s) +O2(g)
-> CO2(g), and
given that delta Hydrogen = -285.8 kj for the rxn.: H2(g)+
1/2O2(g) -> H2O(l), and given
that delta hydrogen = -84.7 kJ for the rxn .: 3H2(g) +2C
+2C(graphite) -> C2H6(g),
calculate the dleta hydrogen for the rxn C2H6(g) + 3 1/2O2(g)
-> 2CO2(g) + 3HO(l)
Delta hydrogen = kJ

When 1.000 g of propane gas (C3H8) is burned at 25ºC and 1.00
atm, H2O (l) and CO2 (g) are formed with the evolution of 50.33 kJ
of energy.
Substance
∆Hºf (kJ mol -1)
Sº (J mol -1 K -1)
H2O (l)
- 285.8
69.95
CO2 (g)
- 393.5
213.7
O2 (g)
0.0
205.0
C3H8 (g)
?
270.2
Calculate the molar enthalpy of combustion, ∆Hºcomb , of propane
and the standard molar enthalpy of formation, ∆Hºf , of propane
gas.

9. Use the following experimentally derived combustion
data to calculate the standard molar enthalpy of formation
(ΔH°f ) of liquid methanol (CH3OH) from its
elements.
2 CH3OH(l) + 3 O2(g) → 2
CO2(g) + 4 H2O(l)
ΔH°rxn = −1452.8 kJ
C(graphite) + O2(g) →
CO2(g)
ΔH°rxn = −393.5 kJ
2 H2(g) + O2(g) → 2
H2O(l)
ΔH°rxn = −571.6 kJ
(1) −238.7 kJ/mol (2) 487.7
kJ/mol (3) −548.3 kJ/mol
(4) 20.1 kJ/mol
(5) 47.1 kJ/mol

Using the following equation for the combustion of octane,
calculate the heat of reaction for 100.0 g of octane. The molar
mass of octane is 114.33 g/mole.
2 C8H18 + 25 O2 -> 16 CO2 + 18 H2O ,deltaH°rxn =
-11018 kJ
I got- 4820kJ but the answer is 4820kJ.
why is the answer positive when the delta h is negative?

Part A
For which of the following reactions is ΔH∘rxn equal to
ΔH∘f of the product(s)?
You do not need to look up any values to answer this
question.
Check all that apply.
Hints
Check all that apply.
S(s)+O2(g)→SO2(g)
Li(s)+12F2(g)→LiF(s)
SO(g)+12O2(g)→SO2(g)
SO3(g)→12O2(g)+SO2(g)
2Li(s)+F2(g)→2LiF(s)
Li(s)+12F2(l)→LiF(s)
Part B
The combustion of propane, C3H8, occurs via the reaction
C3H8(g)+5O2(g)→3CO2(g)+4H2O(g)
with heat of formation values given by the following table:
Substance
ΔH∘f
(kJ/mol)
C3H8 (g)
-104.7
CO2(g)
−393.5
H2O(g)
−241.8
Calculate the enthalpy for...

Given the following reactions and their associated enthalpy
changes
CO2 (g) → C (s) +
O2 (g)
ΔH
= 393.5 kJ
C3H8 (g) + 5 O2 (g) → 3 CO2
(g) + 4 H2O (g) ΔH = -2044 kJ
H2 (g) + 1/2 O2 (g)
→ H2O (g)
ΔH
= -241.8 kJ
calculate the enthalpy change for the following reaction:
4 H2 (g) + 3 C (s)→ C3H8 (g)

Calculate the deltaH for:
CuO (s) + CO (g) ---> Cu(s) + CO2(g)
Given the following thermochemical equations:
2CO (g) + O2(g) --> 2CO2 (g)
deltaH= -566.1kJ
2Cu (s) + O2(g) --> 2CuO(s)
deltaH= -310.5kJ

Octane (C8H18) undergoes combustion according to the following
thermochemical equation:
2C8H18(l) + 25O2(g) 16CO2(g) +
18H2O(l) ∆H°rxn = −10,800
kJ/mol
Given that ∆H°f[CO2(g)] = −394 kJ/mol and ∆H°f[H2O(l)] = −286
kJ/mol, calculate the standard enthalpy of formation of
octane.
a. −326 kJ/mol
b.326 kJ/mol
c.210 kJ/mol
d.-218 kJ/mol

13. Propane burns in air according to the following
equation:
C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (g) ∆H = -2043 kJ
If 5.00 g of propane are reacted at a constant pressure of 1.15
atm leading to a change in volume of +8.6 L, calculate ∆E and the
work done (in kJ). (MM C3H8 = 44.09 g/mol).
Using the information given (∆Hrxn = -2043 kJ) and any needed
values from you text, calculate...

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