Question

**Part A**

Calculate the standard enthalpy change for the reaction

2A+B⇌2C+2D

where the heats of formation are given in the following table:

Substance | ΔH∘f(kJ/mol) |

A | -227 |

B | -399 |

C | 213 |

D | -503 |

Express your answer in kilojoules.

Answer= 273kJ

Part B:

For the reaction given in Part A, how much heat is absorbed when 3.70 mol of A reacts?

Express your answer numerically in kilojoules.

Part C:

For the reaction given in Part A, Δ*S*∘rxn is 25.0 J/K .
What is the standard Gibbs free energy of the reaction,
Δ*G*∘rxn?

Answer #1

A)

we have:

Hof(A) = -227.0 KJ/mol

Hof(B) = -399.0 KJ/mol

Hof(C) = 213.0 KJ/mol

Hof(D) = -503.0 KJ/mol

we have the Balanced chemical equation as:

2 A + B ---> 2 C + 2 D

deltaHo rxn = 2*Hof(C) + 2*Hof(D) - 2*Hof( A) - 1*Hof(B)

deltaHo rxn = 2*(213.0) + 2*(-503.0) - 2*(-227.0) - 1*(-399.0)

deltaHo rxn = 273 KJ

Answer: 273 KJ

B)

From above reaction,

when 2 mol of A reacts, deltaHo rxn = 273 KJ

so, for 3.70 mol, deltaHo rxn = 273*3.70/2 = 505 KJ

Answer: 505 KJ

C)

deltaHo = 273.0 KJ/mol

deltaSo = 25 J/mol.K

= 0.025 KJ/mol.K

T = 298 K

we have below equation to be used:

deltaGo = deltaHo - T*deltaSo

deltaGo = 273.0 - 298.0 * 0.025

deltaGo = 265.55 KJ/mol

Answer: 265.55 KJ/mol

he thermodynamic properties for a reaction are related by the
equation that defines the standard free energy, ΔG∘, in
kJ/mol:
ΔG∘=ΔH∘−TΔS∘
where ΔH∘ is the standard enthalpy change in kJ/mol and
ΔS∘ is the standard entropy change in J/(mol⋅K). A good
approximation of the free energy change at other temperatures,
ΔGT, can also be obtained by utilizing this
equation and assuming enthalpy (ΔH∘) and entropy
(ΔS∘) change little with temperature.
Part A
For the reaction of oxygen and nitrogen to...

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 standard heat...

Part A
Calculate the enthalpy change, ΔH, for the process in
which 44.0 g of water is converted from liquid at 7.6 ∘C to vapor
at 25.0 ∘C .
For water, ΔHvap = 44.0 kJ/mol at 25.0 ∘C and
s = 4.18 J/(g⋅∘C) for H2O(l)
Express your answer numerically in kilojoules.
Part B
How many grams of ice at -11.0 ∘C can be completely converted to
liquid at 9.4 ∘C if the available heat for this process is
5.66×103 kJ...

Calculate the standard enthalpy change for the reaction
2 Al(s) +
Fe2O3(s)
2
Fe(s) + Al2O3(s)
Given that
2 Al(s) + 3/2 O2
(g)
Al2O3(s) ΔH rxn =
-1669.8 kJ/mol
2 Fe (s) +
3/2 O2
(g)
Fe2O3(s) ΔH rxn = -822.2
kJ/mol

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...

1)
Calculate the amount of energy in kilojoules needed to change
207 g of water ice at −10 ∘C to steam at 125 ∘C. The following
constants may be useful:
Cm (ice)=36.57 J/(mol⋅∘C)
Cm (water)=75.40 J/(mol⋅∘C)
Cm (steam)=36.04 J/(mol⋅∘C)
ΔHfus=+6.01 kJ/mol
ΔHvap=+40.67 kJ/mol
Express your answer with the appropriate units.
2) Given the values of ΔH∘rxn, ΔS∘rxn, and
T below, determine ΔSuniv.
Part A
ΔH∘rxn= 90 kJ , ΔSrxn= 144 J/K , T=
304 K
Express your answer using two...

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...

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

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