Question

C_{2}N_{2}O_{2}Hg(s) + O_{2} (g)
-> Hg(g) + 2CO_{2}(g) + N_{2}(g)

Determine the theoretical enthalpy (in kJ/mol) of the mercury
fulminate reaction by using the enthalpy of formation for mercury
fulminate (+ 386 kJ/mol) Remember, ΔH° _{rxn} = Σn x
H°_{f}(products) - Σn x ΔH°_{f}(reactants). Explain
your work. We are assuming a constant pressure situation.

This is can also be termed the ** heat of
explosion**, but when it is termed heat of explosion,
the units are traditionally kJ/kg of substance. Convert your
enthalpy of reaction (kJ/mol) to heat of explosion (kJ/kg) using
the molar mass of your explosive. List that value here and use it
to calculate the explosive energy of 5.00 kg.

Answer #1

The balanced reaction

C2N2O2Hg(s) + O2 (g) = Hg(g) + 2CO2(g) + N2(g)

Enthalpy change for the reaction

ΔH° rxn = ΣH°f(products) - ΣΔH°f(reactants)

= Hf(Hg) + Hf(N2) +2*Hf(CO2) - Hf(O2) - Hf(C2N2O2Hg)

= 61.38 + 0 + 2*(-393.5) - 0 - (386)

ΔH° rxn = - 1111.62 kJ/mol

Heat of explosion = ΔH° rxn / molar mass of C2N2O2Hg

= ( - 1111.62 kJ/mol) / (284.6236 g/mol)

= - ( 3.90557 kJ/g) x (1000g/kg)

= - 3905.57 kJ/kg

For 5 kg explosive

Heat of explosion = (- 3905.57 kJ/kg) x 5 kg

= - 19528 kJ

The standard heat of formation, ΔH∘f, is defined as the
enthalpy change for the formation of one mole of substance from its
constituent elements in their standard states. Thus, elements in
their standard states have ΔH∘f=0. Heat of formation
values can be used to calculate the enthalpy change of any
reaction.
Consider, for example, the reaction
2NO(g)+O2(g)⇌2NO2(g)
with heat of formation values given by the following table:
Substance
ΔH∘f
(kJ/mol)
NO(g)
90.2
O2(g)
0
NO2(g)
33.2
Then the standard heat...

Constants | Periodic Table
Learning Goal:
To understand how standard enthalpy of reaction is related to
the standard heats of formation of the reactants and products.
The standard enthalpy of reaction is the enthalpy change that
occurs in a reaction when all the reactants and products are in
their standard states. The symbol for the standard enthalpy of
reaction is ΔH∘rxn, where the subscript "rxn" stands for
"reaction." The standard enthalpy of a reaction is calculated from
the standard heats...

The standard heat of formation, ΔH∘f, is defined as the
enthalpy change for the formation of one mole of substance from its
constituent elements in their standard states. Thus, elements in
their standard states have ΔH∘f=0. Heat of formation
values can be used to calculate the enthalpy change of any
reaction.
Consider, for example, the reaction
2NO(g)+O2(g)⇌2NO2(g)
with heat of formation values given by the following table:
Substance
ΔH∘f
(kJ/mol)
NO(g)
90.2
O2(g)
0
NO2(g)
33.2
Then the heat of...

The standard heat of formation, ΔH∘f, is defined as the enthalpy
change for the formation of one mole of substance from its
constituent elements in their standard states. Thus, elements in
their standard states have ΔH∘f=0. Heat of formation values can be
used to calculate the enthalpy change of any reaction.
Consider, for example, the reaction
2NO(g)+O2(g)⇌2NO2(g)
with heat of formation values given by the following table:
Substance ΔH∘f
(kJ/mol)
NO(g) 90.2
O2(g) 0
NO2(g) 33.2
Then the standard heat...

The standard heat of formation, ΔH∘f, is defined as the
enthalpy change for the formation of one mole of substance from its
constituent elements in their standard states. Thus, elements in
their standard states have ΔH∘f=0. Heat of formation
values can be used to calculate the enthalpy change of any
reaction.
Consider, for example, the reaction
2NO(g)+O2(g)⇌2NO2(g)
with heat of formation values given by the following table:
Substance
ΔH∘f
(kJ/mol)
NO(g)
90.2
O2(g)
0
NO2(g)
33.2
Then the standard heat...

In a generic chemical reaction involving reactants A and B and
products C and D, aA+bB→cC+dD, the standard enthalpy ΔH∘rxn of the
reaction is given by ΔH∘rxn=cΔH∘f(C)+dΔH∘f(D) −aΔH∘f(A)−bΔH∘f(B)
Notice that the stoichiometric coefficients, a, b, c, d, are an
important part of this equation. This formula is often generalized
as follows, where the first sum on the right-hand side of the
equation is a sum over the products and the second sum is over the
reactants: ΔH∘rxn=∑productsnΔH∘f−∑reactantsmΔH∘f where m and...

1.
Refer to this equation:
2CaCO3 (s) —> 2CaO (s) + 2CO2 (g)
Enthalpy change = -178.1 kJ/ mol reaction
How many grams of CaCo3 must react in order to liberate 545 kJ
of heat?
2. Refer to this equation:
2Al (s) + Fe2O3 (s) —> 2Fe (s) + Al2O3 (s)
Enthalpy change = -847.6 kJ/ mol reaction
How much heat is released if 35.0 g of Al (s) reacts to
completion?

Calculate the standard enthalpy change (ΔH⁰rxn ) for
the reaction of TiCl4(g) and
H2O(g) to form TiO2(s) and
HCl(g) given the standard enthalpies of formation
(ΔH⁰f ) shown in the table below. (Include the sign of the
value in your answer.)
kJ
Compound
ΔH⁰f
(kJ/mol)
TiCl4(g)
−763.2
H2O(g)
−241.8
TiO2(s)
−944.0
HCl(g)
−92.3

What mass of natural gas (CH4) must you burn to emit 275 kJ of
heat?
CH4(g)+2O2(g)→CO2(g)+2H2O(g)ΔH∘rxn=−802.3kJ
m =
Pentane (C5H12) is a component of gasoline that burns according
to the following balanced equation:
C5H12(l)+8O2(g)→5CO2(g)+6H2O(g)
Part A
Calculate ΔH∘rxn for this reaction using standard
enthalpies of formation. (The standard enthalpy of formation of
liquid pentane is -146.8 kJ/mol.)
Express your answer using five significant figures.
ΔH∘rxn =
kJ

Calculate the enthalpy change (ΔrH) for the
reaction below,
N2(g) + 3
F2(g) → 2 NF3(g)
given the bond enthalpies of the reactants and products.
Bond
Bond Enthalpy
(kJ/mol×rxn)
N–N
163
N=N
418
N≡N
945
F–F
155
N–F
283

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