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katrin [286]
3 years ago
13

The standard free energy of formation, ΔG∘f, of a substance is the free energy change for the formation of one mole of the subst

ance from the component elements in their standard states. These values are applicable at 25 ∘C and are found in thermodynamic tables.
The value of ΔG∘f for a substance gives a measure of the thermodynamic stability with respect to the component elements. Negative values for a formation reaction indicate thermodynamic stability of the product. In other words, the compound formed does not spontaneously decompose back into the component elements. Positive values for a formation reaction indicate thermodynamic instability of the product. Thus, the compound will spontaneously decompose, though the rate may be slow.

The sign of ΔG∘f can be used to predict the feasibility of synthesizing a substance from its component elements. The standard free energy change for a reaction, ΔG∘, is a state function and can be calculated from the standard free energies of formation as follows:

ΔG∘rxn=∑npΔG∘f(products)−∑nrΔG∘f(reactants)

where np and nr represent the stoichiometric coefficients in the balanced chemical equation for the reactants and products respectively.

Based on the standard free energies of formation, which of the following reactions represent a feasible way to synthesize the product?

A. N2(g)+H2(g)→N2H4(g); ΔG∘f=159.3 kJ/mol
B. 2Na(s)+O2(g)→Na2O2(s); ΔG∘f=−451.0 kJ/mol
C. 2C(s)+2H2(g)→C2H4(g); ΔG∘f=68.20 kJ/mol
D. 2SO(g)+O2(g)→2SO2(g); ΔG∘f=−600.4 kJ/mol
Chemistry
1 answer:
OLEGan [10]3 years ago
3 0

Answer:

B. 2 Na(s) + O₂(g) → Na₂O₂(s); ΔG∘f=−451.0 kJ/mol

D. 2 SO(g) + O₂(g) → 2 SO₂(g); ΔG°f=−600.4 kJ/mol

Explanation:

The spontaneity of a reaction  is given by the value of the standard Gibbs free energy of the reaction (ΔG°rxn). The more negative is the ΔG°rxn, the more spontaneous is a reaction.

The ΔG°rxn can be calculated using the following expression:

ΔG°rxn = ∑np × ΔG°f(products) − ∑nr × ΔG°f(reactants)

By definition, the standard Gibbs free energy of formation of simple substances in their most stable state is zero. That is why, in the reaction of formation of a compound ΔG°rxn = ΔG°f(product).

<em>Based on the standard free energies of formation, which of the following reactions represent a feasible way to synthesize the product? </em>

<em>     A. N₂(g) + H₂(g) → N₂H₄(g); ΔG°f=159.3 kJ/mol. </em>

<em>     </em>Not feasible. ΔG°rxn = ΔG°f(product) > 0.

    <em>B. 2 Na(s) + O₂(g) → Na₂O₂(s); ΔG°f=−451.0 kJ/mol</em>

    Feasible. ΔG°rxn = ΔG°f(product) < 0.

    <em>C. 2 C(s) + 2 H₂(g) → C₂H₄(g); ΔG°f=68.20 kJ/mol</em>

    Not feasible. ΔG°rxn = ΔG°f(product) > 0.

    <em>D. 2 SO(g) + O₂(g) → 2 SO₂(g); ΔG°f=−600.4 kJ/mol</em>

    Feasible. ΔG°rxn = ΔG°f(product) < 0.

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Rasheed calculates that his chemical reaction should produce 4 moles of product, but when he does the experiment, he gets only 3
Brut [27]

Answer:

The answer to your question is 75%

Explanation:

Data

Theoretical production = 4 moles

Experimental production = 3 moles

Percent yield = ?

Formula

Percent yield = \frac{Experimental production}{Theoretical production} x 100

Substitution

Percent yield = \frac{3}{4} x 100

Result

Percent yield = 75 %

8 0
3 years ago
1. An electric power plant uses energy from burning coal to generate steam at 450 °C. The plant is cooled by 20 °C water
kap26 [50]

Answer:

Explanation:

Efficiency of the electric power plant is e=1-\frac{T_{2}}{T_{1}}

Here Temperature of hot source T_{1} = 450^{o}C=450+273=723 K

and Temperature of sink T_{1} = 20^{o}C=20+273=293 K

Hence the efficiency is  e=1-\frac{293}{723}=0.5947=59.47%

Now another formula for thermal efficiency Is

e_{therm}=\frac{Q_{1}-Q_{2}}{Q_{1}}=\frac{W}{Q_{1}}

Here QI is the of heat taken from source 100 MJ ; Q2 of heat transferred to the sink (river) to be found

W is the of work done and W = QI -Q2

Hence Frome_{therm}=\frac{Q_{1}-Q_{2}}{Q_{1}}=\frac{W}{Q_{1}}

W=e(Q_{1})=(0.5947)(100)=59.47MJ

Hence the of heat transferred to the river Is Q_{2} -W = (100 -59.47=40.53

6 0
3 years ago
A sample of a gas has volume 78.5ml at 318.15 K.. What Volume at will the sample occupy at 273. 15 K when the pressure is held c
DochEvi [55]

Charles’ Law

V₁/T₁=V₂/T₂

78.5/318.15=V₂/273.15

V₂=67.4 ml

7 0
2 years ago
When a lead acid car battery is recharged by the alternator, it acts essentially as an electrolytic cell in which solid lead(II)
lesya692 [45]

Answer: The mass of lead deposited on the cathode of the battery is 1.523 g.

Explanation:

Given: Current = 62.0 A

Time = 23.0 sec

Formula used to calculate charge is as follows.

Q = I \times t

where,

Q = charge

I = current

t = time

Substitute the values into above formula as follows.

Q = I \times t\\= 62.0 A \times 23.0 sec\\= 1426 C

It is known that 1 mole of a substance tends to deposit a charge of 96500 C. Therefore, number of moles obtained by 1426 C of charge is as follows.

Moles = \frac{1426 C}{96500 C/mol}\\= 0.0147 mol

The oxidation state of Pb in PbSO_{4} is 2. So, moles deposited by Pb is as follows.

Moles of Pb = \frac{0.0147}{2}\\= 0.00735 mol

It is known that molar mass of lead (Pb) is 207.2 g/mol. Now, mass of lead is calculated as follows.

No. of moles = \frac{mass}{molar mass}\\ 0.00735 = \frac{mass}{207.2 g/mol}\\mass = 1.523 g

Thus, we can conclude that the mass of lead deposited on the cathode of the battery is 1.523 g.

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3 years ago
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Lapatulllka [165]

Answer:

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Explanation:

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