Question

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

Answer #1

Given

2C8H18(l) + 25O2(g) --> 16CO2(g) + 18H2O(l) ∆H°rxn = −10,800 kJ/mol

The delta H of reaction = Sum of ∆H°f of products - Sum of ∆H°f reactants

So

∆H°rxn = −10,800 kJ/mol = [16X∆H°f CO2 + 18X ∆H°f H2O] - [2X∆H°f C8H18 + 25∆H°f O2]

Note: ∆H°f of elements in their native state = 0 so ∆H°f O2 = 0

−10,800 kJ/mol = [16 X (-394) + 18 ( -286)] - [ 2X∆H°f C8H18]

−10,800 = -11452 - [2X∆H°f C8H18]

652 = - 2X∆H°f C8H18

∆H°f C8H18 = -326 KJ / mole

The combustion of octane, C8H18, proceeds according to the
reaction shown. 2C8H18(l)+25O2(g)⟶16CO2(g)+18H2O(l) If 514 mol of
octane combusts, what volume of carbon dioxide is produced at 38.0
∘C and 0.995 atm?

The octane in gasoline burns according to the following
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produced by the combustion of 5.85 mol of octane? If this reaction
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2C8H18 + 25O2 → 16CO2 + 18H2O ΔH° rxn = -11020 kJ/mol rxn Look
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Combustion of ocane follows the reaction:
2C8H18(l) + 25O2(g) -->
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When
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2C8H18 + 25O2 ->
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Question 4
Part A
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 ΔH°rxn = -11018
kJ
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...

1)
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A)After the reaction, how much octane is left?
2)The Haber-Bosch process is a very important industrial
process. In the Haber-Bosch process, hydrogen gas reacts with
nitrogen gas to produce ammonia according to the equation
3H2(g)+N2(g)→2NH3(g) The
ammonia produced in the Haber-Bosch process has a wide range of
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predicted from the chemical equation. 1.71 g H2 is allowed
to react with...

Using the following equation for the combustion of octane,
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-11018 kJ
I got- 4820kJ but the answer is 4820kJ.
why is the answer positive when the delta h is negative?

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